Qpdf
Description
Description from the project website:
QPDF is a command-line program that does structural, content-preserving transformations on PDF files. (...) 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.
User Experiences
Caron, Bertrand. ‘“Validation OK” They Said: Fixing the Rendering of a So-Called Valid PDF’. Open Preservation Foundation (blog), 21 May 2025. https://openpreservation.org/blogs/validation-ok-they-said-fixing-the-rendering-of-a-so-called-valid-pdf/.
Lindlar, Micky. ‘Trouble-Shooting PDF Validation Errors - a Case of PDF-HUL-38’. Open Preservation Foundation, 27 November 2022. https://openpreservation.org/blogs/trouble-shooting-pdf-validation-errors-a-case-of-pdf-hul-38/.