Changelog:
This is qpdf version 8.2.1. It contains just a new command line flag to
the CLI. There are no library changes from 8.2.0.
This is qpdf version 8.2.0. It contains a few bug fixes and performance
improvements, some minor API enhancements, and a few other small changes.
Changelog:
8.1.0: June 23, 2018
Usability Improvements
When splitting files, qpdf detects fonts and images that the document metadata claims are referenced from a page but are not actually referenced and omits them from the output file. This change can cause a significant reduction in the size of split PDF files for files created by some software packages. Prior versions of qpdf would believe the document metadata and sometimes include all the images from all the other pages even though the pages were no longer present. In the unlikely event that the old behavior should be desired, it can be enabled by specifying --preserve-unreferenced-resources. For additional details, please see Section 3.6, “Advanced Transformation Options”.
When merging multiple PDF files, qpdf no longer leaves all the files open. This makes it possible to merge numbers of files that may exceed the operating system's limit for the maximum number of open files.
The --rotate option's syntax has been extended to make the page range optional. If you specify --rotate=angle without specifying a page range, the rotation will be applied to all pages. This can be especially useful for adjusting a PDF created from a multi-page document that was scanned upside down.
When merging multiple files, the --verbose option now prints information about each file as it operates on that file.
When the --progress option is specified, qpdf will print a running indicator of its best guess at how far through the writing process it is. Note that, as with all progress meters, it's an approximation. This option is implemented in a way that makes it useful for software that uses the qpdf library; see API Enhancements below.
Bug Fixes
Properly decrypt files that use revision 3 of the standard security handler but use 40 bit keys (even though revision 3 supports 128-bit keys).
Limit depth of nested data structures to prevent crashes from certain types of malformed (malicious) PDFs.
In “newline before endstream” mode, insert the required extra newline before the endstream at the end of object streams. This one case was previously omitted.
API Enhancements
The first round of higher level “helper” interfaces has been introduced. These are designed to provide a more convenient way of interacting with certain document features than using QPDFObjectHandle directly. For details on helpers, see Section 6.3, “Helper Classes”. Specific additional interfaces are described below.
Add two new document helper classes: QPDFPageDocumentHelper for working with pages, and QPDFAcroFormDocumentHelper for working with interactive forms. No old methods have been removed, but QPDFPageDocumentHelper is now the preferred way to perform operations on pages rather than calling the old methods in QPDFObjectHandle and QPDF directly. Comments in the header files direct you to the new interfaces. Please see the header files and ChangeLog for additional details.
Add three new object helper class: QPDFPageObjectHelper for pages, QPDFFormFieldObjectHelper for interactive form fields, and QPDFAnnotationObjectHelper for annotations. All three classes are fairly sparse at the moment, but they have some useful, basic functionality.
A new example program examples/pdf-set-form-values.cc has been added that illustrates use of the new document and object helpers.
The method QPDFWriter::registerProgressReporter has been added. This method allows you to register a function that is called by QPDFWriter to update your idea of the percentage it thinks it is through writing its output. Client programs can use this to implement reasonably accurate progress meters. The qpdf command line tool uses this to implement its --progress option.
New methods QPDFObjectHandle::newUnicodeString and QPDFObject::unparseBinary have been added to allow for more convenient creation of strings that are explicitly encoded using big-endian UTF-16. This is useful for creating strings that appear outside of content streams, such as labels, form fields, outlines, document metadata, etc.
A new class QPDFObjectHandle::Rectangle has been added to ease working with PDF rectangles, which are just arrays of four numeric values.
Changelog:
2018-02-25 Jay Berkenbilt <ejb@ql.org>
* 8.0.0: release
2018-02-17 Jay Berkenbilt <ejb@ql.org>
* Fix QPDFObjectHandle::getUTF8Val() to properly handle strings
that are encoded with PDF Doc Encoding. Fixes#179.
* Add qpdf_check_pdf to the "C" API. This method just attempts to
read the entire file and produce no output, making possible to
assess whether the file has any errors that qpdf can detect.
* Major enhancements to handling of type errors within the qpdf
library. This fix is intended to eliminate those annoying cases
where qpdf would exit with a message like "operation for
dictionary object attemped on object of wrong type" without
providing any context. Now qpdf keeps enough context to be able to
issue a proper warning and to handle such conditions in a sensible
way. This should greatly increase the number of bad files that
qpdf can recover, and it should make it much easier to figure out
what's broken when a file contains errors.
* Error message fix: replace "file position" with "offset" in
error messages that report lexical or parsing errors. Sometimes
it's an offset in an object stream or a content stream rather than
a file position, so this makes the error message less confusing in
those cases. It still requires some knowledge to find the exact
position of the error, since when it's not a file offset, it's
probably an offset into a stream after uncompressing it.
* Error message fix: correct some cases in which the object that
contained a lexical error was omitted from the error message.
* Error message fix: improve file name in the error message when
there is a parser error inside an object stream.
2018-02-11 Jay Berkenbilt <ejb@ql.org>
* Add QPDFObjectHandle::filterPageContents method to provide a
different interface for applying token filters to page contents
without modifying the ultimate output.
2018-02-04 Jay Berkenbilt <ejb@ql.org>
* Changes listed on today's date are numerous and reflect
significant enhancements to qpdf's lexical layer. While many
nuances are discussed and a handful of small bugs were fixed, it
should be emphasized that none of these issues have any impact on
any output or behavior of qpdf under "normal" operation. There are
some changes that have an effect on content stream normalization
as with qdf mode or on code that interacts with PDF files
lexically using QPDFTokenizer. There are no incompatible changes
for normal operation. There are a few changes that will affect the
exact error messages issued on certain bad files, and there is a
small non-compatible enhancement regarding the behavior of
manually constructed QPDFTokenizer::Token objects. Users of the
qpdf command line tool will see no changes other than the addition
of a new command-line flag and possibly some improved error
messages.
* Significant lexer (tokenizer) enhancements. These are changes to
the QPDFTokenizer class. These changes are of concern only to
people who are operating with PDF files at the lexical layer using
qpdf. They have little or no impact on most high-level interfaces
or the command-line tool.
New token types tt_space and tt_comment to recognize whitespace
and comments. this makes it possible to tokenize a PDF file or
stream and preserve everything about it.
For backward compatibility, space and comment tokens are not
returned by the tokenizer unless QPDFTokenizer.includeIgnorable()
is called.
Better handling of null bytes. These are now included in space
tokens rather than being their own "tt_word" tokens. This should
have no impact on any correct PDF file and has no impact on
output, but it may change offsets in some error messages when
trying to parse contents of bad files. Under default operation,
qpdf does not attempt to parse content streams, so this change is
mostly invisible.
Bug fix to handling of bad tokens at ends of streams. Now, when
allowEOF() has been called, these are treated as bad tokens
(tt_bad or an exception, depending on invocation), and a
separate tt_eof token is returned. Before the bad token
contents were returned as the value of a tt_eof token. tt_eof
tokens are always empty now.
Fix a bug that would, on rare occasions, report the offset in an
error message in the wrong space because of spaces or comments
adjacent to a bad token.
Clarify in comments exactly where the input source is positioned
surrounding calls to readToken and getToken.
* Add a new token type for inline images. This token type is only
returned by QPDFTokenizer immediately following a call to
expectInlineImage(). This change includes internal refactoring of
a handful of places that all separately handled inline images, The
logic of detecting inline images in content streams is now handled
in one place in the code. Also we are more flexible about what
characters may surround the EI operator that marks the end of an
inline image.
* New method QPDFObjectHandle::parsePageContents() to improve upon
QPDFObjectHandle::parseContentStream(). The parseContentStream
method used to operate on a single content stream, but was fixed
to properly handle pages with contents split across multiple
streams in an earlier release. The new method parsePageContents()
can be called on the page object rather than the value of the
page dictionary's /Contents key. This removes a few lines of
boiler-plate code from any code that uses parseContentStream, and
it also enables creation of more helpful error messages if
problems are encountered as the error messages can include
information about which page the streams come from.
* Update content stream parsing example
(examples/pdf-parse-content.cc) to use new
QPDFObjectHandle::parsePageContents() method in favor of the older
QPDFObjectHandle::parseContentStream() method.
* Bug fix: change where the trailing newline is added to a stream
in QDF mode when content normalization is enabled (the default for
QDF mode). Before, the content normalizer ensured that the output
ended with a trailing newline, but this had the undesired side
effect of including the newline in the stream data for purposes of
length computation. QPDFWriter already appends a newline without
counting in length for better readability. Ordinarily this makes
no difference, but in the rare case of a page's contents being
split in the middle of a token, the old behavior could cause the
extra newline to be interprted as part of the token. This bug
could only be triggered in qdf mode, which is a mode intended for
manual inspection of PDF files' contents, so it is very unlikely
to have caused any actual problems for people using qpdf for
production use. Even if it did, it would be very unusual for a PDF
file to actually be adversely affected by this issue.
* Add support for coalescing a page's contents into a single
stream if they are represented as an array of streams. This can be
performed from the command line using the --coalesce-contents
option. Coalescing content streams can simplify things for
software that wants to operate on a page's content streams without
having to handle weird edge cases like content streams split in
the middle of tokens. Note that
QPDFObjectHandle::parsePageContents and
QPDFObjectHandle::parseContentStream already handled split content
streams. This is mainly to set the stage for new methods of
operating on page contents. The new method
QPDFObjectHandle::pipeContentStreams will pipe all of a page's
content streams though a single pipeline. The new method
QPDFObjectHandle.coalesceContentStreams, when called on a page
object, will do nothing if the page's contents are a single
stream, but if they are an array of streams, it will replace the
page's contents with a single stream whose contents are the
concatenation of the original streams.
* A few library routines throw exceptions if called on non-page
objects. These constraints have been relaxed somewhat to make qpdf
more tolerant of files whose page dictionaries are not properly
marked as such. Mostly exceptions about page operations being
called on non page objects will only be thrown in cases where the
operation had no chance of succeeding anyway. This change has no
impact on any default mode operations, but it could allow
applications that use page-level APIs in QPDFObjectHandle to be
more tolerant of certain types of damaged files.
* Add QPDFObjectHandle::TokenFilter class and methods to use it to
perform lexical filtering on content streams. You can call
QPDFObjectHandle::addTokenFilter on stream object, or you can call
the higher level QPDFObjectHandle::addContentTokenFilter on a page
object to cause the stream's contents to passed through a token
filter while being retrieved by QPDFWriter or any other consumer.
For details on using TokenFilter, please see comments in
QPDFObjectHandle.hh.
* Enhance the string, type QPDFTokenizer::Token constructor to
initialize a raw value in addition to a value. Tokens have a
value, which is a canonical representation, and a raw value. For
all tokens except strings and names, the raw value and the value
are the same. For strings, the value excludes the outer delimiters
and has non-printing characters normalized. For names, the value
resolves non-printing characters. In order to better facilitate
token filters that mostly preserve contents and to enable
developers to be mostly unconcerned about the nuances of token
values and raw values, creating string and name tokens now
properly handles this subtlety of values and raw values. When
constructing string tokens, take care to avoid passing in the
outer delimiters. This has always been the case, but it is now
clarified in comments in QPDFObjectHandle.hh::TokenFilter. This
has no impact on any existing code unless there's some code
somewhere that was relying on Token::getRawValue() returning an
empty string for a manually constructed token. The token class's
operator== method still only looks at type and value, not raw
value. For example, string tokens for <41> and (A) would still be
equal because both are representations of the string "A".
* Add QPDFObjectHandle::isDataModified method. This method just
returns true if addTokenFilter has been called on the stream. It
enables a caller to determine whether it is safe to optimize away
piping of stream data in cases where the input and output are
expected to be the same. QPDFWriter uses this internally to skip
the optimization of not re-compressing already compressed streams
if addTokenFilter has been called. Most developers will not have
to worry about this as it is used internally in the library in the
places that need it. If you are manually retrieving stream data
with QPDFObjectHandle::getStreamData or
QPDFObjectHandle::pipeStreamData, you don't need to worry about
this at all.
* Provide heavily annoated examples/pdf-filter-tokens.cc example
that illustrates use of some simple token filters.
* When normalizing content streams, as in qdf mode, issue warning
about bad tokens. Content streams are only normalized when this is
explicitly requested, so this has no impact on normal operation.
However, in qdf mode, if qpdf detects a bad token, it means that
either there's a bug in qpdf's lexer, that the file is damaged, or
that the page's contents are split in a weird way. In any of those
cases, qpdf could potentially damage the stream's contents by
replacing carrige returns with newlines or otherwise messing with
spaces. The mostly likely case of this would be an inline image's
compressed data being divided across two streams and having the
compressed data in the second stream contain a carriage return as
part of its binary data. If you are using qdf mode just to look at
PDF files in text editors, this usually doesn't matter. In cases
of contents split across multiple streams, coalescing streams
would eliminate the problem, so the warning mentions this. Prior
to this enhancement, the chances of qdf mode writing incorrect
data were already very low. This change should make it nearly
impossible for qdf mode to unknowingly write invalid data.
2018-02-04 Jay Berkenbilt <ejb@ql.org>
* Add QPDFWriter::setLinearizationPass1Filename method and
--linearize-pass1 command line option to allow specification of a
file into which QPDFWriter will write its intermediate
linearization pass 1 file. This is useful only for debugging qpdf.
qpdf creates linearized files by computing the output in two
passes. Ordinarily the first pass is discarded and not written
anywhere. This option allows it to be inspected.
---------------------
2014-06-07 Jay Berkenbilt <ejb@ql.org>
* 5.1.2: release
* MS Visual C++ build: explicitly target Windows 5.0.1 (XP)
* New example program: pdf-split-pages: efficiently split PDF
files into individual pages.
* Bug fix: don't fail on files that contain streams where /Filter
or /DecodeParms references a stream. Before, qpdf would try to
convert these to direct objects, which would fail because of the
stream.
2014-02-22 Jay Berkenbilt <ejb@ql.org>
* Bug fix: if the last object in the first part of a linearized
file had an offset that was below 65536 by less than the size of
the hint stream, the xref stream was invalid and the resulting file
is not usable. This is now fixed.
2014-01-14 Jay Berkenbilt <ejb@ql.org>
* 5.1.1: release
2013-12-26 Jay Berkenbilt <ejb@ql.org>
* Bug fix: when copying foreign objects (which occurs during page
splitting among other cases), avoid traversing the same object
more than once if it appears more than once in the same direct
object. This bug is performance-only and does not affect the
actual output.
2013-12-17 Jay Berkenbilt <ejb@ql.org>
* 5.1.0: release
2013-12-16 Jay Berkenbilt <ejb@ql.org>
* Document and make explicit that passing null to
QUtil::setRandomDataProvider() resets the random data provider.
* Provide QUtil::getRandomDataProvider().
2013-12-14 Jay Berkenbilt <ejb@ql.org>
* Allow anyspace rather than just newline to follow xref header.
This allows qpdf to read a wider range of damaged files.
2013-11-30 Jay Berkenbilt <ejb@ql.org>
* Allow user-supplied random data provider to be used in place of
OS-provided or insecure random number generation. See
documentation for 5.1.0 for details.
* Add configure option --enable-os-secure-random (enabled by
default). Pass --disable-os-secure-random or define
SKIP_OS_SECURE_RANDOM to avoid attempts to use the operating
system-provided secure random number generation. This can be
especially useful on Windows if you wish to avoid any dependency
on Microsoft's cryptography system.
2013-11-29 Jay Berkenbilt <ejb@ql.org>
* If NO_GET_ENVIRONMENT is #defined, for Windows only,
QUtil::get_env will always return false. This was added to
support a user who needs to avoid calling GetEnvironmentVariable
from the Windows API. QUtil::get_env is not used for any
functionality in qpdf and exists only to support the test suite
including test coverage support with QTC (part of qtest).
* Add /FS to msvc builds to allow parallel builds to work with
Visual C++ 2013.
* Add missing #include <algorithm> in some files that use std::min
and std::max.
2013-11-21 Jay Berkenbilt <ejb@ql.org>
* Change image comparison tests, which are disabled by default, to
use tiff files with 8 bits per sample rather than 4. This works
around a bug in tiffcmp but also increases time and disk space for
image comparison tests.
2013-10-28 Jay Berkenbilt <ejb@ql.org>
* Fix MacOS compilation errors by adding a missing #include
<string> in a header file.
2013-10-18 Jay Berkenbilt <ejb@ql.org>
* 5.0.1: release
* Warn when -accessibility=n is specified with a modern encryption
format (R > 3). Also, accept this flag (and ignore with warning)
with 256-bit encryption. qpdf has always ignored the
accessibility setting with R > 3, but it previously did so
silently.
2013-10-05 Jay Berkenbilt <ejb@ql.org>
* Replace operator[] in std::string and std::vector with "at" in
order to get bounds checking. This reduces the chances that
incorrect code will result in data exposure or buffer overruns.
See README.hardening for additional notes.
* Use cryptographically secure random number generation when
available. See additional notes in README.
* Replace some assert() calls with std::logic_error exceptions.
Ideally there shouldn't be assert() calls outside of testing.
This change may make a few more potential code errors in handling
invalid data recoverable.
* Security fix: In places where std::vector<T>(size_t) was used,
either validate that the size parameter is sane or refactor code
to avoid the need to pre-allocate the vector. This reduces the
likelihood of allocating a lot of memory in response to invalid
data in linearization hint streams.
* Security fix: sanitize /W array in cross reference stream to
avoid a potential integer overflow in a multiplication. It is
unlikely that any exploits were possible from this bug as
additional checks were also performed.
* Security fix: avoid buffer overrun that could be caused by bogus
data in linearization hint streams. The incorrect code could only
be triggered when checking linearization data, which must be
invoked explicitly. qpdf does not check linearization data when
reading or writing linearized files, but the qpdf --check command
does check linearization data.
* Security fix: properly handle empty strings in
QPDF_Name::normalizeName. The empty string is not a valid name
and would never be parsed as a name, so there were no known
conditions where this method could be called with an empty string.
* Security fix: perform additional argument sanity checks when
reading bit streams.
* Security fix: in QUtil::toUTF8, change bounds checking to avoid
having a pointer point temporarily outside the bounds of an
array. Some compiler optimizations could have made the original
code unsafe.
2013-07-10 Jay Berkenbilt <ejb@ql.org>
* 5.0.0: release
* 4.2.0 turned out to be binary incompatible on some platforms
even though there were no changes to the public API. Therefore
the 4.2.0 release has been withdrawn, and is being replaced with a
5.0.0 release that acknowledges the ABI change and also removes
some problematic methods from the public API.
* Remove methods from public API that were only intended to be
used by QPDFWriter and really didn't make sense to call from
anywhere else as they required internal knowledge that only
QPDFWriter had:
- QPDF::getLinearizedParts
- QPDF::generateHintStream
- QPDF::getObjectStreamData
- QPDF::getCompressibleObjGens
- QPDF::getCompressibleObjects
2013-07-07 Jay Berkenbilt <ejb@ql.org>
* 4.2.0: release [withdrawn]
* Ignore error case of a stream's decode parameters having invalid
length when there are no stream filters.
* qpdf: add --show-npages command-line option, which causes the
number of pages in the input file to be printed on a line by
itself.
* qpdf: allow omission of range in --pages. If range is omitted
such that an argument that is supposed to be a range is an invalid
range and a valid file name, the range of 1-z is assumed. This
makes it possible to merge a bunch of files with something like
qpdf --empty out.pdf --pages *.pdf --
2013-06-15 Jay Berkenbilt <ejb@ql.org>
* Handle some additional broken files with missing /ID in trailer
for encrypted files and with space rather than newline after xref.
2013-06-14 Jay Berkenbilt <ejb@ql.org>
* Detect and correct /Outlines dictionary being a direct object
when linearizing files. This is not allowed by the spec but has
been seen in the wild. Prior to this change, such a file would
cause an internal error in the linearization code, which assumed
/Outlines was indirect.
* Add /Length key to crypt filter dictionary for encrypted files.
This key is optional, but some version of MacOS reportedly fail to
open encrypted PDF files without this key.
* Bug fix: properly handle object stream generation when the
original file has some compressible objects with generation != 0.
* Add QPDF::getCompressibleObjGens() and deprecate
QPDF::getCompressibleObjects(), which had a flaw in its logic.
* Add new QPDFObjectHandle::getObjGen() method and indiciate in
comments that its use is favored over getObjectID() and
getGeneration() for most cases.
* Add new QPDFObjGen object to represent an object ID/generation
pair.
2013-04-14 Jay Berkenbilt <ejb@ql.org>
* 4.1.0: release
2013-03-25 Jay Berkenbilt <ejb@ql.org>
* manual/qpdf-manual.xml: Document the casting policy that is
followed in qpdf's implementation.
2013-03-11 Jay Berkenbilt <ejb@ql.org>
* When creating Windows binary distributions, make sure to only
copy DLLs of the correct type. The ensures that the 32-bit
distributions contain 32-bit DLLs and the 64-bit distributions
contain 64-bit DLLs.
2013-03-07 Jay Berkenbilt <ejb@ql.org>
* Use ./install-sh (already present) instead of "install -c" to
install executables to fix portability problems against different
UNIX variants.
2013-03-03 Jay Berkenbilt <ejb@ql.org>
* Add protected terminateParsing method to
QPDFObjectHandle::ParserCallbacks that implementor can call to
terminate parsing of a content stream.
2013-02-28 Jay Berkenbilt <ejb@ql.org>
* Favor fopen_s and strerror_s on MSVC to avoid CRT security
warnings. This is useful for people who may want to use qpdf in
an application that is Windows 8 certified.
* New method QUtil::safe_fopen to wrap calls to fopen. This is
less cumbersome than calling QUtil::fopen_wrapper.
* Remove all calls to sprintf
* New method QUtil::int_to_string_base to convert to octal or
hexademical (or decimal) strings without using sprintf
2013-02-26 Jay Berkenbilt <ejb@ql.org>
* Rewrite QUtil::int_to_string and QUtil::double_to_string to
remove internal length limits but to remain backward compatible
with the old versions for valid inputs.
2013-02-23 Jay Berkenbilt <ejb@ql.org>
* Bug fix: properly handle overridden compressed objects. When
caching objects from an object stream, only cache objects that,
based on the xref table, would actually be resolved into this
stream. Prior to this fix, if an object stream A contained an
object B that was overridden by an appended section of the file,
qpdf would cache the old value of B if any non-overridden member
of A was accessed before B. This commit fixes that bug.
2013-01-31 Jay Berkenbilt <ejb@ql.org>
* Do not remove libtool's .la file during the make install step.
Note to packagers: if your distribution wants to you remove the
.la file, you will have to do that yourself now.
2013-01-25 Jay Berkenbilt <ejb@ql.org>
* New method QUtil::hex_encode to encode binary data as a
hexadecimal string
* qpdf --check was exiting with status 0 in some rare cases even
when errors were found. It now always exits with one of the
document error codes (0 for success, 2 for errors, 3 or warnings).
2013-01-24 Jay Berkenbilt <ejb@ql.org>
* Make --enable-werror work for MSVC, and generally handle warning
options better for that compiler. Warning flags for that compiler
were previous hard-coded into the build with /WX enabled
unconditionally.
* Split warning flags into WFLAGS in autoconf.mk to make them
easier to override. Before they were repeated in CFLAGS and
CXXFLAGS and were commingled with other compiler flags.
* qpdf --check now does syntactic checks all pages' content
streams as well as checking overall document structure. Semantic
errors are still not checked, and there are no plans to add
semantic checks.
2013-01-22 Jay Berkenbilt <ejb@ql.org>
* Add QPDFObjectHandle::getTypeCode(). This method returns a
unique integer (enumerated type) value corresponding to the object
type of the QPDFObjectHandle. It can be used as an alternative to
the QPDFObjectHandle::is* methods for type testing, particularly
where there is a desire to use a switch statement or optimize for
performance when testing object types.
* Add QPDFObjectHandle::getTypeName(). This method returns a
string literal describing the object type. It is useful for
testing and debugging.
2013-01-20 Jay Berkenbilt <ejb@ql.org>
* Add QPDFObjectHandle::parseContentStream, which parses the
objects in a content stream and calls handlers in a callback
class. The example pdf-parse-content illustrates it use.
* Add QPDF_Operator and QPDF_InlineImage types along with
appropriate wrapper methods in QPDFObjectHandle. These new object
types are to facilitate content stream parsing.
QPDF is a command-line program that does structural, content-preserving
transformations on PDF files. It could have been called something
like pdf-to-pdf. It also provides many useful capabilities to
developers of PDF-producing software or for people who just want
to look at the innards of a PDF file to learn more about how they
work.
QPDF is capable of creating linearized (also known as web-optimized)
files and encrypted files. It is also capable of converting PDF
files with object streams (also known as compressed objects) to
files with no compressed objects or to generate object streams from
files that don't have them (or even those that already do). QPDF
also supports a special mode designed to allow you to edit the
content of PDF files in a text editor. For more details, please
see the documentation links below.
QPDF includes support for merging and splitting PDFs through the
ability to copy objects from one PDF file into another and to
manipulate the list of pages in a PDF file. The QPDF library also
makes it possible for you to create PDF files from scratch. In this
mode, you are responsible for supplying all the contents of the
file, while the QPDF library takes care off all the syntactical
representation of the objects, creation of cross references tables
and, if you use them, object streams, encryption, linearization,
and other syntactic details.
QPDF is not a PDF content creation library, a PDF viewer, or a
program capable of converting PDF into other formats. In particular,
QPDF knows nothing about the semantics of PDF content streams. If
you are looking for something that can do that, you should look
elsewhere. However, once you have a valid PDF file, QPDF can be
used to transform that file in ways perhaps your original PDF
creation can't handle. For example, programs generate simple PDF
files but can't password-protect them, web-optimize them, or perform
other transformations of that type.
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