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PDF Forgeries Are Surprisingly Rare (2022)

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TZubiri · 1790050311 · focus · HN ↗
>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.
1. eru · 1790050571 · focus · HN ↗
  Gwern is talk about editing an existing pdf. Less so about creating one from scratch.
mjg59 · 1790050393 · focus · HN ↗
Not quite the scenario described (it wasn't an academic paper), but <a href="https://mjg59.dreamwidth.org/73317.html" rel="nofollow">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!
1. arjvik · 1790050874 · focus · HN ↗
  was linked in the article!
2. anitil · 1790051410 · focus · HN ↗
  I believe it's actually linked in the OP about half way down. What a crazy thing for an agent to do - to turn a minor disagreement into a maybe-crime.
3. jstanley · 1790062078 · focus · HN ↗
  Are you saying that RightSignature puts the checksum information inside the document and therefore destroys the checksum? What is the thinking behind that?
eru · 1790050804 · focus · HN ↗
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"
1. black_knight · 1790062069 · focus · HN ↗
  Typos are so easy to weed out these days, I assume including them is a stylistic choice.
  1. eru · 1790405484 · focus · HN ↗
    Gwern fixed it in the meantime. So presumably it was not a stylistic choice.
55555 · 1790050875 · focus · HN ↗
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.
1. cenamus · 1790051643 · focus · HN ↗
  Are you talking about vapes?
2. 3eb7988a1663 · 1790052344 · focus · HN ↗
  I have no sense of gwen's readership numbers, but I find it unlikely that one rather erudite blog has anything to do with global nicotine consumption. People have been smoking for centuries. The vaping industry had guerilla marketing campaigns to target college kids.
  No rain drop thinks it is responsible for the flood, but I am hard-pressed to think a blog article greatly swayed hearts and minds.
3. dudisubekti · 1790052625 · focus · HN ↗
  <a href="https://gwern.net/nicotine" rel="nofollow">https://gwern.net/nicotine
  This one?
  It seems to be listing the pros and cons of nicotine and is well-sourced...
  What "damage" do you see caused by this article?
  1. simoncion · 1790056762 · focus · HN ↗
    Yeah, once you remove the hazards inherent in cigarette and/or cigar smoking from the discussion, the only solid objection I've heard to nictotine consumption is that it's probably more addictive than caffeine.
    I understand why personal vaporizer use was demonized, but -goddamn- that's going to be a public health disaster only an order of magnitude or two smaller than when folks started demonizing nuclear power back in the mid 1900's.
    mschuster91 · 1790059307 · focus · HN ↗
    > the only solid objection I've heard to nictotine consumption is that it's probably more addictive than caffeine.
    s/probably/massively. You don't see ads and public health messages for quitting coffee, you don't see bans for coffee advertising, but you do see a whole lot of things aimed at reducing or quitting nicotine products.
    lelanthran · 1790060925 · focus · HN ↗
    > You don't see ads and public health messages for quitting coffee, you don't see bans for coffee advertising,
    You would if coffee has the same probability of causing cancer as smoking.
    Being addictive on its own is rarely a reason to demonise a substance. The addictive substances that are demonised are always those that also have negative health effects, even in moderation (like smoking).
    simoncion · 1790061066 · focus · HN ↗
    > You don't see ads and public health messages for quitting coffee, you don't see bans for coffee advertising...
    That'd be because -unlike cigarette and cigar smoking- coffee doesn't create a substantially elevated risk of cancer.
    Had we had the tech for personal nicotine vaporizers back in the 1600s and retained it until today, I very strongly expect that -other than the "Drugs of all kinds are bad!" moralizers- you'd not see much of that sort of concern.
    > Besides, nicotine withdrawal is utter hell.
    Waaaay back when when I quit cold turkey after smoking for a couple of years I was very grouchy and irritable (and knew that a cigarette would fix it) for like a week. That was it. I've not tried nicotine vaporizers, but I'd be interested to see if -given similarly sized nicotine doses- quitting vaporized nicotine after a couple of years is as annoying as quitting cigarettes was.
    > Caffeine withdrawal usually is solved by a night of good healthy sleep...
    That tells me that you haven't gone through serious caffeine withdrawal. The effects from quitting caffeine cold turkey last for less time, but way more unpleasant than quitting cigarettes.
    vablings · 1790088374 · focus · HN ↗
    As an avid consumer of both nicotine and caffeine I can say a few things.
    Caffeine is way worse for me, the days that I consume zero caffeine I pretty much always end up with a migrate and minor. If I don't use my vaporizer, I get mildly irritated by not having it around but no prominent physiological effects
    simoncion · 1790107460 · focus · HN ↗
    > ...I pretty much always end up with a migrate and minor.
    Minor what?
    And yeah, two things:
    1) It's telling that -despite the fact that the closest store that I get my coffee and tea from also sells cigarettes (and that I'm so obviously old that they don't ask me for ID, so that minor inconvenience isn't a factor)- I've been able to quit nicotine, but never able to quit caffeine.
    2) I can't even count the number of times I've consumed a mug of tea or coffee for no other reason than to avoid withdrawal symptoms. Cigarettes were never like that. Just like caffeine, I inevitably developed a tolerance... but working through nicotine withdrawal was annoying, rather than _painful_.
    vablings · 1790174336 · focus · HN ↗
    Ironically, I wrote that post with a migraine. Migraine and a minor headache are what I meant to say.
    There are lots of yummy drinks that contain caffeine which is a shame for those quitting but a boon for myself, I personally like the taste of redbull much to my dentists dismay
4. aaron695 · 1790054708 · focus · HN ↗
  [dead]
5. mock-possum · 1790056887 · focus · HN ↗
  Really? I don’t see anything objectionable in the article - and ‘an entire generation??’ How do you figure?
6. DonHopkins · 1790072575 · focus · HN ↗
  [delayed]
tristanj · 1790052487 · focus · HN ↗
I think a big reason for this is that PDF editing tools are just pretty terrible.
PDFs are meant to be 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. 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.
1. slybot · 1790053332 · focus · HN ↗
  PDF's are not Presentation Document Format. Should be "Portable".
  1. slybot · 1790055717 · focus · HN ↗
    Good to see you change it from "PDFs are Presentation Document Format" => "PDFs are meant to be a presentation document format". Next time, don't forget edit log..
  2. ozim · 1790070810 · focus · HN ↗
    Main point of parent still stands - PDF's are not meant to be edited one should generate new from the source material and that's it.
  3. marysol5 · 1790076503 · focus · HN ↗
    They're "portable" in that they can be "universally" read. Not that you can create and manage them.
2. mamonoleechi · 1790073587 · focus · HN ↗
  >I think a big reason for this is that PDF editing tools are just pretty terrible.
  Inkscape is a pretty good tool to edit .pdfs
  when you import a regular .pdf, it needs to convert it once, and once saved, you can edit the pdf and work on it as if it was a regular .svg
  if you choose to embed the fonts when saving, .pdf files becomes easy to work on, you don't even need to export them.
  1. jolmg · 1790115448 · focus · HN ↗
    Was skeptical but curious. Depends on your expectations, I guess. It's no MS Office Word / LibreOffice Writer. With a 650-page document, takes some time to open it (few minutes?) or even edit text once open, even on a beefy machine. It's double-click to highlight a word and it takes 5-6 solid seconds. The line segments of the tables are separate rectangles, so the right border of a 4 row table is 6 rectangles with the corners being separate ones. The text is presented one block of text, but there's no autowrap, and pressing Enter for some reason brings the rest of the line to the start of the same line, rather than the next, with the lines below not moving at all.
    Trying LO Writer on the same file is much more pleasant. Opens far more quickly. The text is more manageable, though each line of paragraphs are their separate text boxes. Tables still have the same problem.
3. marysol5 · 1790076468 · focus · HN ↗
  Editing PDF's is worse than editing documents in Microsoft Word!
  Even generating them on the fly can be a real pain. I had a workflow when I was out of work to auto-generate a CV based upon re-writing sections to match the spec. So I'd have pre-written blocks and slot them in. And yet, somehow, even then it would break formatting all over the place.
exmadscientist · 1790054169 · focus · HN ↗
The flip side to this is that when you do come across a forged PDF (and I have!), they can be really, really effective. Nobody expects them. There are usually tells in the metadata, but... there don't have to be.
sjtgraham · 1790054407 · focus · HN ↗
I agree that you won't find forged PDF documents in the wild with any type of frequency, but they are forged in private settings. Forged or doctored bank statements are relatively more common. FinCEN identifies altered bank statements alongside W-2s, tax returns, gift letters, and employment information as examples of documents involved in mortgage fraud [1]. In March 2026, a mortgage loan officer was even charged by federal prosecutors with altering and creating bank statements to make borrowers appear qualified for a mortgage [2].
[1] <a href="https://www.fincen.gov/mortgage-loan-fraud" rel="nofollow">https://www.fincen.gov/mortgage-loan-fraud
[2] <a href="https://www.justice.gov/usao-mdfl/pr/licensed-mortgage-loan-officer-charged-bank-fraud" rel="nofollow">https://www.justice.gov/usao-mdfl/pr/licensed-mortgage-loan-...
1. yieldcrv · 1790063145 · focus · HN ↗
  I saw it alot in the fake KYC world, phantom commodities trades
  and all those things listed wouldn’t be prosecuted, as long as you don’t touch mortgages
  I would say KYC in general is a joke and nobody cares, as long as FinCEN and the DOJ believe KYC is working. But as far as the peddling of forged PDF’s go, very common, just not at the point of where the more damaging crime occurs ….. except in mortgage fraud, where that crime explicitly considers the fake employment letter to be the crime
2. rithdmc · 1790072137 · focus · HN ↗
  I can't find the quote any more, but when some internal bank workers were done for laundering money (possibly the Estonian branch of Danske Bank), one of the messages between the defendants read "There's always photoshop" :)
creatonez · 1790055537 · focus · HN ↗
> (Or better yet: upload it directly to Libgen/Sci-Hub and let everyone else redistribute it.)
Can this actually be done without an ISBN or DOI number?
1. gwern · 1790056153 · focus · HN ↗
  Yes. Libgen/Sci-Hub have minimal metadata requirements. And they especially do not require ISBNs/DOIs because there are an incredible number of documents out there with neither one. It would be absurd to ban all pre-1970 books, and lots of journals to this day don't bother issuing DOIs.
bbor · 1790058440 · focus · HN ↗
Ok this one actually baffles me -- anyone have the energy to explain what I'm missing? The repeated concern about forged scientific papers doesn't really track, but that's what academic institutions are for, at least in part.
If someone were to share a preprint PDF that I don't believe, my instinct would be to double-check it against the institution associated with its publication. If it was never published then it's basically just a screenshot of a blog post.
Ohhh okay the opening makes more sense now. The blog above is publishing papers in form of blog posts as a protest against scientific publishing. I love the energy, but ruminating on how weird it is that so few people take advantage of the thing that you're weird for doing in the first place feels... obtuse?
rickdeckard · 1790061732 · focus · HN ↗
> "And when you do find a PDF claiming something malicious, [..] it’s always a ‘new’ PDF, which is forthright about it being a new unpublished ‘white paper’ or somesuch, and doesn’t purport to be a published paper."
> "Whereas, if you were so epistemically careless with images on, say, Facebook, you would wind up with a folder stuffed full of lying images which have been Photoshopped, claimed to be things other than what they are, ‘deep faked’, etc"
Maybe because a paper is a comprehending medium, expecting the reader to understand its source and interpret the content on a more intellectual level, whereas effective images/videos are usually framed to be understood immediately.
i.e. if I want to convince people that lizard-people live among us and I want to manufacture proof, my demographic probably responds more to images with a lizard than a reinterpreted academic paper...
[deleted] · 1790061871 · focus · HN ↗
[deleted]
arethuza · 1790063041 · focus · HN ↗
Forged and modified PDFs were definitely a problem in some commercial areas that I used to work in (this was about 15 years ago).
1. reddalo · 1790068891 · focus · HN ↗
  They still are. I know some people who got software packages for free because they "proved" to be university students by submitting a forged PDF.
  1. zarzavat · 1790070235 · focus · HN ↗
    Why commit copyright infringement when you could commit criminal fraud instead?!
    dist-epoch · 1790070847 · focus · HN ↗
    Sometimes the software is just not available online, or it doesn't work well if cracked.
    Students giving out free Microsoft licenses they could access through their University to people they knew was a thing, because Microsoft activation hacks had all kinds of problems.
2. cucumber3732842 · 1790071667 · focus · HN ↗
  There are obscene amounts of "forged" stamped surveys and engineering drawings floating around.
  Not like altering lines or anything material (I can already imagine the breathless replies being typed) but changing text to remove references that would indicate other survey work was done that they don't wanna submit to public record, changing a labeled distance by a couple feet to make something that already exists technically compliant.
  Like with everything else it's the little guys sticking their necks out. The big guys can afford good surveyors who "get it" don't need to be told when a difference within the bounds of measurement error will have four or five figure implications.
laserbeam · 1790071762 · focus · HN ↗
I'd say the reason for this is that PDFs are not viral like images or videos. I don't think any of the technical arguments are strong enough.
If you want to forge a PDF, you do it because you have a private target in mind. Financial fraud, corporate espionage... There are other settings but people don't just share PDFs around for you to see a deluge of fake ones.
1. rithdmc · 1790072415 · focus · HN ↗
  I believe that some of the DNC (and other hack & leak) documents were tampered with. Does anyone remember if that included pdfs?
  1. marysol5 · 1790076723 · focus · HN ↗
    One was a word doc they added "Confidential" to the footer, then released as PDF
DonHopkins · 1790073880 · focus · HN ↗
[dead]
karol · 1790074091 · focus · HN ↗
I read this and classified as "future issue". If it's so easy as the author described it will happen, or it's already happening and it will be discovered much later.
The Dieselgate is a good analogy. Incentives, how easy it is to get to profit.
broken-kebab · 1790078077 · focus · HN ↗
PDFs are being forged everyday, mostly for financial incentives. The reason it rarely happens with scienific papers (as seems to be a particular concern of the author) is because it makes not much practical sense.
1. General public don't read papers.
2. General public have lowered trust to them.
3. It's not impossible to produce and publish genuine paper with forged data.
ValdikSS · 1790088950 · focus · HN ↗
There's entire industry to detect PDF forgeries. They analyze how exactly each software acts upon editing the file and detect these features.
Some software rewrap the page into say additional XObject, some add unique elements, some change one IDs but not the others.
I had a great blog post about it but can't find it right now. Will post if find the link.
pvaldes · 1790103514 · focus · HN ↗
Modify any extant PDF is surprisingly easy. Write in your favorite "something"-tex, modify at will, convert to pdf.
Most people just never understand how powerful can be TeX and fear this path, because it takes a long training and the investment in time is huge. But you don't need to master all the details to do simple text replacements or filling a form with your name and address. That part can be learned in a day, and is totally free.
bluebxrry · 1790143868 · focus · HN ↗
If the signature matters both parties pay for Acrobat-approved certificates. In most other situations I like to imagine a world where we agree to a document before signing it, thus the signing is just a formality or even optional.

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