Could look into using exiftool, qpdf or pdftk, if you are comfortable with the terminal ✨
qpdf is very powerful. If OP is comfortable with the terminal, I'd recommend qpdf.
I would try reprinting the PDFs and comparing the hashes afterwards. That should remove any metadata in the headers as new headers are created.
That wouldn't work for something like Pathfinder PDFs from the Paizo website. They add a text watermark with the name and email associated with your account on their site to each page of the document. It's not metadata, it's actual data
Why would the checksum differ between downloads if there was a watermark with user identifiable data
Just checked one of my Paizo pdfs and in addition to my account name and email address it also has the datetime that I downloaded the pdf written in the watermark. Presumably because they append the file creation time when the pdf is being signed
Fair, then reprinting won't help. I'd go ahead and come up with some Python script which exported all pages as png, edited that specific portion of every image and recompile it to a pdf. I'm not sure if there is a too which could already do that out-of-the-box.
Unfortunately then you lose things like text and links. I think the only real solution for my specific example (which to be clear, might not be OP's dilemma) is to crack and directly edit the binary data of the PDF file
Maybe print the book via print to pdf and check again.
Wow… The amount of information already being shared here is outstanding! Keep on rowing/patching mates
If you're on Linux, Metadata Cleaner might work. https://flathub.org/apps/fr.romainvigier.MetadataCleaner
Okay hear me out... physically print the documents then, using a high resolution scanner, make a digital copy and finally use a raster to vector convertor.
I know this is probably dumb, but I just wanted to throw this out there.
Why not just print it to PDF. It doesn't lose any data, plus it doesn't take ages to scan the books.
Exiftool can remove metadata. There might even be websites that can handle this.
Perhaps printing to pdf may work
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