I think a big reason for this is that PDF editing tools are just pretty terrible.

PDFs are a Presentation Document Format, not an Editable Document Format. I have some experience editing PDFs, and it's difficult to make significant modifications. Editing small sections of text or replacing a date is fine, but once you try to start editing entire paragraphs or changing the layout, it quickly becomes unmanageable. The kerning looks weird, the spacing between words looks off, and when you look into it you realize the the sentence you're trying to edit is actually split across a dozen text objects. I've seen cases where every word is its own text object, even split within the words. For these it becomes almost impossible to edit without destroying the spacing, so you just give up.

And the approved way to edit these PDFs is via Adobe Acrobat Pro, which costs $20/month (ugh), which I'm not willing to pay for.

So I think this is why we just don't see that many PDF forgeries. The editing tools just aren't very good. Maybe it's different now we can just ask Claude to edit our PDFs for us.

Not quite the scenario described (it wasn't an academic paper), but https://mjg59.dreamwidth.org/73317.html is my experience of dealing with a forged PDF. Part of the reason it's rare is that it's actually very hard to do it well!

Offtopic but the damage caused to an entire generation by Gwern's nicotine article is truly astounding. Obviously he's not responsible for the actions of others and it was written with good intentions but wow.

Gwern, in case you are reading this, there's a typo in:

> (In the rare cases anyone tampers with PDFs, it quickly turns into a technical morass and he-said-she-said, and requires several orders of magnitude more effort to prove than to do; consider the hoops epxperts had to jump through in the Craig Wright cases, or even just a landlord editing a contract—where the contract was done through a digital document timestamping service!)

Specifically "epxperts"

>PDF forgery is striking because it’d be so easy to do: find a useful research paper, edit it in any of the many PDF utilities, upload anywhere, wait for people to copy it (as they do), then take down yours; now you have an authoritative peer-reviewed research paper floating around the Internet with no links to you, in the perfect crime. (Or better yet: upload it directly to Libgen/Sci-Hub and let everyone else redistribute it.)

Seen as (unsigned) PDFs are basically images of documents, it's wild to claim that there are no forgeries, anyone doing a good ole fake document, fake diploma, fake wire transfer, fake articles of incorporation, etc... is using a pdf for faking. A nigerian prince scam sending an attachment mentioning 15.000.000$ locked up in inheritance would constitute a PDF forgery.