PDFedit

PDF editing library, GUI application, and command-line tools for viewing and directly editing the internal structure of PDF documents — raw objects, streams, and cross-reference tables — rather than just visual page content. Particularly useful for inspecting and repairing malformed or non-standard PDFs that better-behaved editors refuse to open. A Flatpak build is available for running it on modern Linux distributions despite the project itself being unmaintained since 2020.

Licensed GPLv2.