PDF4QT

(c) Jakub Melka 2018-2026

[email protected]

https://jakubmelka.github.io/

This software is consisting of PDF rendering library, and several applications, such as advanced document viewer, command line tool, and document page manipulator application. Software is implementing PDF functionality based on PDF Reference 2.0. It is written and maintained by Jakub Melka.

Software works on Microsoft Windows / Linux.

Software is provided without any warranty of any kind.

Should you find this software beneficial, your support would be greatly appreciated :heart: Sponsor!

1. ACKNOWLEDGEMENTS

This software is based in part on the work of the Independent JPEG Group.

Portions of this software are copyright © 2019 The FreeType Project (www.freetype.org). All rights reserved.

2. LEGAL ISSUES

This software was originally licensed under the GNU Lesser General Public License version 3 (LGPLv3). As of April 27, 2025, the project has been relicensed under the MIT License by the original author. The change to the MIT License was made to provide greater freedom and flexibility for both open-source and commercial use, reduce legal complexity, and encourage broader adoption and contribution.

Please see the attached LICENSE.txt file for details.

This software also uses several third-party libraries, and users must comply with the licenses of those third-party components.

3. FEATURES

Software have following features (the list is not complete):

• multithreading support
• encryption
• color management
• optional content handling
• text layout analysis
• signature validation
• annotations
• form filling
• text to speech capability
• editation
• file attachments
• optimalization (compressing documents)
• command line tool
• audio book conversion
• internal structure inspector
• compare documents
• static XFA support (readonly, simple XFA only)
• electronically/digitally sign documents
• public key security encryption
• OCR - text recognition of scanned documents with a searchable invisible text layer (Tesseract)

4. THIRD PARTY LIBRARIES

Several third-party libraries are used.

1. libjpeg, see https://www.ijg.org/
2. FreeType, see https://www.freetype.org/index.html, FTL license used
3. OpenJPEG, implementing Jpeg2000, see https://www.openjpeg.org/, 2-clause MIT license
4. Qt, https://www.qt.io/, LGPL license used
5. OpenSSL, https://www.openssl.org/, Apache 2.0 license
6. LittleCMS, http://www.littlecms.com/
7. zlib, https://zlib.net/
8. Blend2D, https://blend2d.com/
9. Tesseract OCR, https://github.com/tesseract-ocr/tesseract, Apache 2.0 license (optional, see PDF4QT_ENABLE_OCR)
10. Leptonica, http://www.leptonica.org/, BSD 2-clause license (dependency of Tesseract)
11. Tesseract language models (tessdata_fast / tessdata_best), https://github.com/tesseract-ocr/tessdata_fast, Apache 2.0 license

5. CONTRIBUTIONS

Contributions are welcome!

Since the project is now licensed under the MIT License, contributions can be freely submitted without the need to sign a Contributor License Agreement (CLA). However, all contributions must be made under the terms of the MIT License to ensure license consistency across the project.

You are encouraged to contribute by testing, offering feedback, providing advice, or submitting code improvements.

6. INSTALLING

Windows

The Release page lists binaries for Windows, both with and without an installer.

Arch Linux

A pdf4qt-git package is available in the AUR.

Linux - Flatpak/AppImage

For other Linux distributions, there are two options available. A Flatpak package can be accessed at Flathub. Alternatively, an AppImage is available in the Releases section. The AppImage format is designed to work on nearly all Linux systems. Historically, a .deb package was also offered, but it has been discontinued due to compatibility issues with some Linux distributions. The executable names are: Pdf4QtEditor, Pdf4QtDiff, Pdf4QtLaunchPad, Pdf4QtPageMaster, Pdf4QtViewer, and PdfTool.

7. COMPILING

This software can be compiled on both Windows and Linux. A compiler supporting the C++20 standard is needed.

On Windows, you can use Visual Studio 2022 or MinGW.

On Linux, a GCC version >= 8 should work, altough we tested it with GCC 11.

Compiling from sources

1. Install vcpkg

    git clone https://github.com/Microsoft/vcpkg.git
    ./vcpkg/bootstrap-vcpkg.sh -disableMetrics
    VCPKG_ROOT=$(pwd)/vcpkg
   

   Check that vcpkg path is correct: $VCPKG_ROOT/vcpkg --version.

2. Build PDF4QT

   2.1 Clone repo

    git clone https://github.com/JakubMelka/PDF4QT
    cd PDF4QT
   

   2.2 Configure

    cmake -B build -S . -DPDF4QT_INSTALL_QT_DEPENDENCIES=0 -DCMAKE_TOOLCHAIN_FILE=$VCPKG_ROOT/scripts/buildsystems/vcpkg.cmake -DCMAKE_INSTALL_PREFIX='/' -DCMAKE_BUILD_TYPE=Release
   

   (One user reported success with -DCMAKE_INSTALL_PREFIX='' instead, as otherwise all there paths were prepended with /usr (causing /usr/usr...

   For a debug build, append -DCMAKE_BUILD_TYPE=Debug.

   It is recommended to set the VCPKG_OVERLAY_PORTS variable to 'PDF4QT/vcpkg/overlays' to prevent crashes due to the incompatible LIBPNG library on some Linux systems.

   2.3 Build

    cmake --build build
   

   Use the -j switch to build multiple files in parallel.

   2.4 Install

    sudo cmake --install build
   

   To uninstall, run sudo xargs rm < ./build/install_manifest.txt.

Using Qt Creator (both Windows/Linux)

1. Download Qt 6.9 or higher, and VCPKG package manager (https://vcpkg.io/en/index.html)
2. Open Qt Creator and configure the project
3. Build

CMAKE Compilation Options

Several important compilation options are available and should be set before building. On Windows, CMake can prepare a Wix project to create a *.msi installer package.

Option	Platform	Description
PDF4QT_INSTALL_MSVC_REDISTRIBUTABLE	Windows	Includes MSVC redistributable in installation
PDF4QT_INSTALL_PREPARE_WIX_INSTALLER	Windows	Prepare .msi installator using Wix installer
PDF4QT_INSTALL_DEPENDENCIES	Any	Install dependent libraries into installation directory
PDF4QT_INSTALL_QT_DEPENDENCIES	Any	Install Qt dependent libraries into installation directory
VCPKG_OVERLAY_PORTS	Linux	Set it to prevent crashes with incompatible libpng library
PDF4QT_ENABLE_OCR	Any	Build the OCR feature (Tesseract engine), ON by default

Following important variables should be set or checked before any attempt to compile this project:

Variable	Platform	Description
PDF4QT_QT_ROOT	Any	Qt installation directory
QT_CREATOR_SKIP_VCPKG_SETUP	Any	Enable or disable automatic vcpkg setup
CMAKE_PROJECT_INCLUDE_BEFORE	Any	Should be set to package manager auto setup
CMAKE_TOOLCHAIN_FILE	Any	Should be set to toolchain
CMAKE_BUILD_TYPE	Any	Can be Release (default) or Debug

Sample setup on Windows

Following set of variables gives sample setup for MS Windows. It is minimal initial configuration to be able to built Debug build on MS Windows.

Key	Value
CMAKE_BUILD_TYPE	Debug
CMAKE_CXX_COMPILER	%{Compiler:Executable:Cxx}
CMAKE_C_COMPILER	%{Compiler:Executable:C}
CMAKE_GENERATOR	Ninja
CMAKE_PREFIX_PATH	%{Qt:QT_INSTALL_PREFIX}
CMAKE_PROJECT_INCLUDE_BEFORE	%{IDE:ResourcePath}/package-manager/auto-setup.cmake
CMAKE_TOOLCHAIN_FILE	%{Qt:QT_INSTALL_PREFIX}/lib/cmake/Qt6/qt.toolchain.cmake
PDF4QT_QT_ROOT	C:/Programming/Qt/6.4.0/msvc2019_64
QT_QMAKE_EXECUTABLE	%{Qt:qmakeExecutable}

Tested Compilers - Windows

• Visual Studio 2022 (Microsoft Visual C++ Compiler 17.1)
• MinGW 11.2.0

Tested Compilers - Linux

• GCC 13.1.1

8. DISCLAIMER

I wrote this project in my free time. I hope you will find it useful!