PoDoFo

1. What is PoDoFo?
2. Features
3. Requirements
4. Licensing
5. Development quickstart
6. Doxygen Documentation
7. Software life cycle and API stability
8. String encoding and buffer conventions
9. Thread safety
10. PoDoFo tools
11. TODO
12. FAQ
13. No warranty
14. Contributions
15. Authors

What is PoDoFo?

PoDoFo is a free portable C++ library to work with the PDF file format.

PoDoFo provides classes to parse a PDF file and modify its content, allowing to write
it back to disk easily. Besides PDF parsing and manipulation PoDoFo also provides
facilities to create your own PDF files from scratch.

Features

PoDoFo has a modern and user-friendly C++17 API that features:

• PDF parsing with high-level entity inspection (annotations, form fields and others)
• PDF writing with support for incremental updates
• PDF signing with PAdES-B compliance,
  RSA/ECDSA encryption and asynchronous/deferred signing
• Text drawing with automatic CID encoding generation and font subsetting
• Full-featured low-level Unicode text extraction
• Advanced CJK language support (text extraction and automatic multi-byte encoding)
• PDF/A compliance preservation (e.g., font embedding, simultaneous PDF/A and PDF/UA compliance)
• PDF/UA compliance preservation (e.g., when adding annotations/form fields)
• Deferred font file data embedding

PoDoFo does not support rendering PDF content yet. Text writing
is also limited as it currently does not perform proper text shaping/kerning.

Requirements

To build PoDoFo lib you'll need a c++17 compiler,
CMake 3.23 and the following libraries (tentative minimum versions indicated):

• freetype2 (2.11)
• fontconfig (2.13.94, required for Unix platforms, optional for Windows)
• OpenSSL (1.1 and 3.0 are supported)
• LibXml2 (2.9.12)
• zlib
• libjpeg (9d, optional)
• libtiff (4.0.10, optional)
• libpng (1.6.37, optional)

For the most popular toolchains, PoDoFo requires the following
minimum versions:

• msvc++ 14.16 (VS 2017 15.9)
• gcc 9.0
• clang/llvm 9.0
• XCode 11.0

It is regularly tested with the following IDE/toolchains versions:

• Visual Studio 2022 17.14
• gcc 9.3.1
• XCode 15.4
• NDK r28

Licensing

The PoDoFo library is licensed under the LGPL 2.0 or later terms or, at your option, MPL 2.0.

PoDoFo tools are licensed under the GPL 2.0 or later terms.

Please refer to the NOTICE file for the use of 3rd party components. Consider disabling the AFDKO integration if you plan to distribute the PoDoFo library with GPL 2.0-only projects.

Development quickstart

PoDoFo is known to compile through a multitude of package managers (including APT, brew, vcpkg, Conan), and has public continuous integration working in Ubuntu Linux, MacOS and
Windows, bootstrapping the CMake project, building and testing the library. It's highly recommended to build PoDoFo using such package managers.

There's also a playground area in the repository where you can have
access to pre-built dependencies for some popular architectures/operating systems:
the playground is the recommended setting to develop the library and reproduce bugs,
while it's not recommended for the deployment of your application using PoDoFo.
Have a look to the Readme there.

Warning: PoDoFo is known to be working in cross-compilation toolchains (eg. Android/iOS development), but support may not provided in such scenarios. If you decide to manually build dependencies you are assumed to know how to identity possible library clashes/mismatches and how to deal with compilation/linking problems that can arise in your system.

Build with APT

From the source root run:

sudo apt install -y libfontconfig1-dev libfreetype-dev libxml2-dev libssl-dev libjpeg-dev libpng-dev libtiff-dev
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Debug ..
cmake --build . --config Debug

Build with brew

Install brew, then from the source root run:

brew install fontconfig freetype openssl libxml2 jpeg-turbo libpng libtiff cmake
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_FIND_FRAMEWORK=NEVER -DCMAKE_PREFIX_PATH=`brew --prefix` -DFontconfig_INCLUDE_DIR=`brew --prefix fontconfig`/include -DOPENSSL_ROOT_DIR=`brew --prefix openssl@3` ..
cmake --build . --config Debug

Build with Conan

Install conan, then from source root run:

mkdir build
cd build
conan install ..
cmake -DCMAKE_BUILD_TYPE=Debug ..
cmake --build . --config Debug

Build with vcpkg

Follow the vcpkg quickstart guide to setup the package manager repository first.
In Windows, it may be also useful to set the environment variable VCPKG_DEFAULT_TRIPLET to x64-windows to default installing 64 bit dependencies
and define a VCPKG_ROOT variable with the location of the repository as created in the quickstart.

Then from source root run:

vcpkg install
mkdir build
cmake "-DCMAKE_TOOLCHAIN_FILE=vcpkg.cmake" -DCMAKE_BUILD_TYPE=Debug -B build
cmake --build build --config Debug

Consume PoDoFo from package managers with CMake

Starting with version 1.0, PoDoFo has a quite advanced CMake integration and can be consumed
as a CMake package.
As soon as it's correctly integrated in your favorite package manager (APT, vcpkg, Conan,
...), you will be able to locate PoDoFo and compile your application with the following
CMakeLists.txt:

cmake_minimum_required(VERSION 3.23)

project(PoDoFoSample)

# PoDoFo public header requires at least C++17,
# but it can be used with higher standards
set(CMAKE_CXX_STANDARD 23)

# If you are not using a package manager and/or you
# are installing PoDoFo to a non-standard path
#list(APPEND CMAKE_PREFIX_PATH "/path/to/podofo_install_dir")

find_package(PoDoFo 1.0.0 REQUIRED)
message(STATUS "Found PoDoFo: ${PoDoFo_VERSION}")

add_executable(helloworld main.cpp)
target_link_libraries(helloworld podofo::podofo)

CMake switches

• PODOFO_BUILD_TEST: Build the unit tests, defaults to TRUE;

• PODOFO_BUILD_EXAMPLES: Build the examples, defaults to TRUE;

• PODOFO_BUILD_UNSUPPORTED_TOOLS: Build the PoDoFo tools, defaults to FALSE. See
  the relevant section in the Readme;

• PODOFO_BUILD_LIB_ONLY: If TRUE, it will build only the library component.
  This unconditionally disable building tests, examples and tools;

• PODOFO_BUILD_STATIC: If TRUE, build the library as a static object and use it in tests,
  examples and tools. By default a shared library is built;

• PODOFO_WITH_FONTMANAGER: Enable search of fonts in the system. It generally requires Fontconfig, unless specific platforms fallbacks are enabled. Defaults to ON;

• PODOFO_WITH_WIN32GDI_FONT_SEARCH: In Windows, enable use of Win32 GDI for font search (Fontconfig is always prefered, if available), defaults to OFF;

• PODOFO_WITH_AFDKO: Enable the Adobe Font Development Kit for OpenType integration (used in Type1/OpenType font subsetting), defaults to ON;

• PODOFO_DEVENDOR_TCBSPAN: If TRUE, the tcb::span library will be devendored;

• PODOFO_DEVENDOR_DATE: If TRUE, the date library will be devendored;

• PODOFO_DEVENDOR_FASTFLOAT: If TRUE, the fast_float library will be devendored;

• PODOFO_DEVENDOR_FMT: If TRUE, the fmt library will be devendored;

• PODOFO_DEVENDOR_FMT_HEADER_ONLY: Implies PODOFO_DEVENDOR_FMT, but uses the fmt::fmt-header-only library flavour;

• PODOFO_DEVENDOR_UTF8CPP: If TRUE, the utf8cpp library will be devendored;

• PODOFO_DEVENDOR_UTF8PROC: If TRUE, the utf8proc library will be devendored.

Static linking

If you want to use a static build of PoDoFo and you are including the PoDoFo cmake project it's very simple. Do something like the following in your CMake project:

set(PODOFO_BUILD_LIB_ONLY TRUE CACHE BOOL "" FORCE)
set(PODOFO_BUILD_STATIC TRUE CACHE BOOL "" FORCE)
add_subdirectory(podofo)
# ...
target_link_libraries(MyTarget podofo::podofo)

If you are linking against a precompiled static build of PoDoFo this is a scenario where the support is limited, as you are really supposed to be able to identify and fix linking errors. The general steps are:

• Add PODOFO_STATIC compilation definition to your project, or before including podofo.h;
• Link the libraries podofo.a, podofo_private.a, podofo_3rdparty.a (podofo.lib, podofo_private.lib, podofo_3rdparty.lib in MSVC) and all the dependent libraries.

Doxygen Documentation

The API documentation can be found at https://podofo.github.io/podofo/documentation/ .

Generate the doxygen documentation

1. Prerequisite: Ensure you have Doxygen installed on your machine. If not, visit Doxygen's official website to download and install it.

2. Generating Documentation: After completing the build process detailed in the Development quickstart chapter, navigate to the root directory of PoDoFo's source code.
   Open a terminal or command prompt and run the following command:

   bashCopy
   doxygen build/Doxyfile

3. Viewing the Documentation: Once the documentation generation completes, you'll find a documentation directory that contains the generated documentation. Open index.html in your favorite web browser to view the API documentation.

   bashCopy
   cd build/doxygen/documentation
   open index.html

Software life cycle and API stability

Refer to the main article in the Wiki.
At this page you can find an incomplete guide on migrating 0.9.8 code to 0.10.x, and from 0.10.x to 1.0.

String encoding and buffer conventions

All std::strings or std::string_view in the library are intended
to hold UTF-8 encoded string content. PdfString and PdfName constructors
accept UTF-8 encoded strings by default (PdfName accept only characters in the
PdfDocEncoding char set, though). charbuff and bufferview
instead represent a generic octet buffer.

Thread safety

For the most part PoDoFo is not a thread safe library. As a general rule: use any object on the same thread it was created on.
Alternatively: guard access to objects obtained through a PdfDocument using a mutex. Explicit support is provided for freeing
object instances in different threads, as is done in modern garbage collected languages.

PoDoFo Tools

Warning: Tools are currently unsupported, untested and unmaintained.

PoDoFo tools are still available in the source tree
but their compilation is disabled by default because they are unsted/unmaintained,
and will not receive support until their status is cleared. It's not recommended to include them in software distributions.
If you want to build them make sure to bootstrap the CMake project with -DPODOFO_BUILD_UNSUPPORTED_TOOLS=TRUE.
Tools are conveniently enabled in the playground
at least to ensure library changes won't break their compilation.

TODO

There's a TODO list, or look
at the issue tracker.

FAQ

Q: PoDoFo compilation requires a CMake version higher than what is present in my system, can you lower the requirement?<a id='faq-cmake'></a>

A: No, CMake 2.23 introduced a functionality that makes it very easy to create CMake packages that
is too convenient to ignore. In Windows it's easy to upgrade the CMake version to latest, while in MacOS it's the same thanks to the official KitWare installer or brew.
In a linux system it's also quite easy to install an upgraded parallel CMake installation. Just run the following script:

export CMAKE_VERSION=3.31.7 \
    && wget -nv https://github.com/Kitware/CMake/releases/download/v${CMAKE_VERSION}/cmake-${CMAKE_VERSION}-Linux-x86_64.sh \
    && chmod +x cmake-${CMAKE_VERSION}-Linux-x86_64.sh \
    && ./cmake-${CMAKE_VERSION}-Linux-x86_64.sh --prefix=/usr/local --skip-license \
    && rm cmake-${CMAKE_VERSION}-Linux-x86_64.sh \
    && cmake --version

Q: How do I sign a document?<a id='faq-sign'></a>

A: PoDoFo HEAD now supplies a high level signing procedure which is very powerful
and that allows to sign a document without having to supply a CMS structure manually.
By default, it supports signing a document with the modern PAdES-B
compliance profiles, but there's also a support for the legacy PKCS7 signatures.
Providing you have both ASN.1 encoded X509 certificate and RSA private key, you
can sign a document with the following code:

cppCopy
auto inputOutput = std::make_shared<FileStreamDevice>(filepath, FileMode::Open);

PdfMemDocument doc;
doc.Load(inputOutput);

auto& page = doc.GetPages().GetPageAt(0);
auto& signature = page.CreateField<PdfSignature>("Signature", Rect());

auto signer = PdfSignerCms(x509certbuffer, pkeybuffer);
PoDoFo::SignDocument(doc, *inputOutput, signer, signature);

There's also a support for external signing services and/or signing the document
in memory buffers. See the various signing examples in the unit tests.

Q: Can I still use an event based procedure to sign the document?<a id='faq-sign-event-based'></a>

A: Yes, the old low level procedure hasn't changed and it's still available.
To describe the procedure briefly, one has to fully Implement a PdfSigner,
retrieve or create a PdfSignature field, create an output device (see next question)
and use PoDoFo::SignDocument(doc, device, signer, signature). When signing,
the sequence of calls of PdfSignature works in this way: method PdfSigner::Reset()
is called first, then the PdfSigner::ComputeSignature(buffer, dryrun) is called with
an empty buffer and the dryrun argument set to true. In this call one can just
resize the buffer overestimating the required size for the signature, or just
compute a fake signature that must be saved on the buffer. Then a sequence of
PdfSigner::AppendData(buffer) are called, receiving all the document data to
be signed. A final PdfSigner::ComputeSignature(buffer, dryrun) is called, with
the dryrun parameter set to false. The buffer on this call is cleared (capacity
is not altered) or not accordingly to the value of PdfSigner::SkipBufferClear().

Q: PdfMemDocument::SaveUpdate() or PoDoFo::SignDocument() write only a
partial file: why there's no mechanism to seamlessly handle the incremental
update as it was in PoDoFo 0.9.x? What should be done to correctly update/sign
the document?<a id='faq-manual-update'></a>

A: The previous mechanism in PoDoFo 0.9.x required enablement of document
for incremental updates, which is a decision step which I believe should be
unnecessary. Also:

1. In case of file loaded document it still required to perform the update in
   the same file, and the check was performed on the path of the files being
   operated to, which is unsafe;
2. In case of buffers worked for one update/signing operation but didn't work
   for following operations, meaning the mechanism was bugged/unreliable.

An alternative strategy that makes clearer the fact that the incremental update
must be performed on the same file from where the document was loaded, or that underlying
buffer will grow its memory consumption following subsequent operations in case of
buffer loaded documents, is available. It follows a couple of examples showing the
correct operations to update a document, loaded from file or buffer:

1. Save an update on a file loaded document, by loading and saving the document on the same location:

cppCopy
auto inputOutput = std::make_shared<FileStreamDevice>(filename, FileMode::Open);

PdfMemDocument doc;
doc.Load(inputOutput);

doc.SaveUpdate(*inputOutput);

2. Save an update on a buffer, by copying the source first to the buffer
   that will be also used to load the document:

cppCopy
charbuff outputBuffer;
FileStreamDevice input(filepath);
auto inputOutput = std::make_shared<BufferStreamDevice>(outputBuffer);
input.CopyTo(*inputOutput);

PdfMemDocument doc;
doc.Load(inputOutput);

doc.SaveUpdate(*inputOutput);

Signing documents can be done with same technique, read the other questions for more examples.

Q: Can I sign a document a second time?<a id='faq-sign-second'></a>

A: Yes, this is tested, but to make sure this will work you'll to re-parse the document a second time,
as reusing the already loaded document is still untested (this may change later). For example you can
do as it follows:

cppCopy
auto inputOutput = std::make_shared<FileStreamDevice>(filepath, FileMode::Open);

{
    PdfMemDocument doc;
    doc.Load(inputOutput);
    auto& page = doc.GetPages().GetPageAt(0);
    auto& signature = page.CreateField<PdfSignature>("Signature1", Rect());

    PdfSignerCms signer(x509certbuffer, pkeybuffer);
    PoDoFo::SignDocument(doc, *inputOutput, signer, signature);
}

{
    PdfMemDocument doc;
    doc.Load(inputOutput);
    auto& page = doc.GetPages().GetPageAt(0);
    auto& signature = page.CreateField<PdfSignature>("Signature2", Rect());
    PdfSignerCms signer(x509certbuffer, pkeybuffer);
    PoDoFo::SignDocument(doc, *inputOutput, signer, signature);
}

No warranty

PoDoFo may or may not work for your needs and comes with absolutely no
warranty. Serious bugs, including security flaws, may be fixed at arbitrary
timeframes, or not fixed at all. Priority of implementing new features
and bug fixing are decided according to the interests and personal
preferences of the maintainers. If you need PoDoFo to integrate a feature
or bug fix that is critical to your workflow, the most welcome and fastest
approach is to contribute
high-quality patches.

Contributions

Please subscribe to the project mailing list
which is still followed by several of the original developers of PoDoFo.
A Discord server has also been created to ease some more informal chatter.
If you find a bug and know how to fix it, or you want to add a small feature, you're welcome to send a pull request,
providing it follows the coding style
of the project. As a minimum requisite, any contribution should be:

• valuable for a multitude of people and not only self relevant for the contributor;
• consistent with surrounding code and not result in unpredictable behavior and/or bugs.

Other reasons for the rejection, or hold, of a pull request may be:

• the proposed code is incomplete or hacky;
• the change doesn't fit the scope of PoDoFo;
• the change shows lack of knowledge/mastery of the PDF specification and/or C++ language;
• the change breaks automatic tests performed by the maintainer;
• general lack of time in reviewing and merging the change.

If you need to implement a bigger feature or refactor, ask first if
it was already planned. The feature may be up for grabs, meaning that it's open for external contributions.
Please write in the relevant issue that you started to work on that, to receive some feedback/coordination.
If it's not, it means that the refactor/feature is planned to be implemented later by the maintainer(s).
If the feature is not listed in the issues, add it and/or create a discussion
to receive some feedback and discuss some basic design choices.

Authors

Warning: Please don't use personal email addresses for technical support inquries, but create
github issues instead.

PoDoFo is currently developed and maintained by
Francesco Pretto, together with Dominik Seichter and others. See the file
AUTHORS.md for more details.