In any case, some researchers have claimed that Sci-Hub obtained their credentials through phishing. I don't know if it's true but in any case, such claims provide plausible deniability against that kind of watermarking proof, don't they ?

> Both hidden and conspicuous watermarks are common in trade book PDF downloads

https://github.com/kanzure/pdfparanoia

Does only Crossref do this?

I'm asking because a friend of mine who's enrolled in 2 colleges, just downloaded the same scholarly PDF (one that's also available through sci-hub) with 2 different college credentials and they had the same sha256sum.

Then when he tried it through sci-hub, he also got the same sha256sum.

Crossref doesn't do anything at all in relation to SciHub or watermarking PDFs. We don't host content. (I'm happy to talk about what we do do, but it's off-topic)

Sorry if my disclaimer wasn't clear. I was just pointing out affiliation as standard on HN.

Nah, that doesn't work for academic papers. You usually access them anonymously anyway through your institution (which has a subscription). So even if they watermark (and I don't think they do), they can only watermark the institution.

There are plenty of instances of big-name publishers sending nastygrams to whole institutions and/or cutting them off for perceived abuse.

In that case the institution should unsubscribe and point their members to sci-hub.