I know Calibre can remove DRM, but it seems that Calibre does not remove things like watermarks, references to the buyer by name, etc. Now maybe I can try to find those manually, but that is an error prone process. Plus, what if they embed a unique digital signature that ties back to me? I understand that this is a very uncommon practice, but I do not want to find myself in a bad place.
I suppose the only way to remove a digital signature of any sort is to buy two of the same e-book by different people, diff them, and remove anything that differentiates them.
Is there any tool that does this or automates the process? am I being too paranoid, and this is not a real threat?
The bad news is that uploading e-books will involve programming on your part (for your sanity at least).
The good news is that it should be far easier than other mediums.
If you are approaching from a complete safety perspective (cause you live in a fiefdom that owes tribute to the publishers guild), then you're going to want to OCR the pages of the book and use the text to make a brand new book free from metadata. I'm pretty sure a python crash course could get you up and running in a month or 6.
If you want what's closest to the original product, then you'll need a python script that strips everything from the book into just a text document, then re-convert back into your own book. You'll have to review the text document to see if any random code was included in the book like invisible text.
Both options are so simple from a programming perspective that I've never seen scripts to strip e-book protections. A real (the solution is left un-worked as a challenge for the reader). And from what I know, the publishers have switched to focusing on selling hard copies as their bread and butter, and striking deals with libraries for other revenue. Big money is still in mandatory university textbooks.
Source: Never actually done what you're asking for
Thanks for your advice. I am a programmer by craft so I can definitely do that. I think the only issue may be books with any important content that is not text, i.e. graphics and images (and unfortunately, many of the books I am interested in have that). If I understood what you said correctly.
Pymupdf has options to handle images. Good package.
gImageReader or ocrmypdf will get you the pdf text, but after the text will need fiddling with and cleaning. Use LibreOffice, languagetool, write-good, etc to make finding the oddballs easy.
pdftk is what you want for editing pdf metadata.
Gimp is what you'll need for editing images, Looking for watermarks, smoothing edges, lowering quality, introducing random noise, etc.
exiftool is what you'll need for image metadata. Or take a screenshot, add a bit of noise or de-noise, and add back to the new pdf.
Scrivener or LibreOffice if you want to polish/republish, though that's a ton of work.
Even with OCR, couldn't your copy at least in theory be laced with strategically placed minor word changes? Say throughout the book you pick 30 spots to change a word without changing the meaning of the text, or you introduce a typo. If every copy gets a different set of those that would be a unique identifier.
I think I have heard that being done with imperceptable changes in films sent for showings in theaters.
@matcha_addict@lemy.lol In this situation, I'd advise acquiring a copy from an alternative source, then just compare the texts of the two.
In practicality though, if you're already going the OCR route then just utility knife cut the pages from a real book and feed them into a feeder scanner. All they get to know is that some asshole cyberpunk script kiddie jacked your book while you were waiting at a bus stop.