PDFium is an open-source PDF rendering engine: https://pdfium.googlesource.com/pdfium/
This repository contains build scripts for Linux and Windows, to build a custom patched version of PDFium that can be used with the GDAL PDF driver. This is a slightly modified version of the PDFium sources, for GDAL needs.
Tested with Ubuntu 16.04 x86_64 with development packages for zlib, libjpeg, libpng, and other development tools (git)
Run ./build_linux.sh.
It will generate the install/ directory with the end products: header files and libpdfium.a needed to build the GDAL PDF driver
Tested with Windows 10, with Visual Studio 2017 community edition, x86_64 build. Windows 10 SDK 10.0.19041.0 with the "Debugging Tools for Windows SDK 10" must also be installed.
Run "git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git" from this repository, which will create a depot_tools subdirectory.
Then run "git checkout d1580d53b7bc1f244d4eaf797aca0d066fad166c" in that subdirectory.
Run build_win.bat from cmd.exe with the environment variables set for the compiler you use (VS 2017 or 2019) (or from the "x64 Native tools Command Prompt for VS2017" entry)
Note: if the console remains stuck on the stage """Downloading CIPD client for windows-amd64 from https://chrome-infra-packages.appspot.com/client?platform=windows-amd64&version=git_revision:0323cbe1ef467af36aa6784f2315c5ee36e89e34...""" and multiple error messages mentionning it can not be downloaded, just manually download the file at the above URL, rename it as .cipd_client.exe in the depot_tools directory and re-run build_win.bat
It will generate the install/ directory with the end products: header files and pdfium.lib needed to build the GDAL PDF driver.
Pre-build binaries may be found at https://github.com/rouault/pdfium_build_gdal_3_2/releases