> PDFs are a bad way of communicating information.

They have the strength of one PDF being frozen & (mostly) treated online as immutable - compared to a webpage which might change, or a blog post which might be edited. If a PDF needs to be replaced there'll be a notice.

And the single-file nature of PDFs makes them more likely to sit in an archive not managed by the author (vs a blog) so they tend to live as long as the archive rather than the author's blog.

For something that needs to Be referenced by others those are useful properties - I'd argue they outweigh how good PDF is at communicating information.