About 90° rotated tables: Sometimes only the text in the headers are rotated. Sometimes not to 90°, but some arbitrary value.

And then there are digital signatures. 5 years ago I looked into automatically verifying signed documents. Either there are multiple competing standards on how to sign a PDF or my government (Austria) just invented their own for the heck of it. Could not figure out to verify those signatures. Our government provides a website where you can upload such a PDF so they verify it for you. Yeah, sure. Nice try. The source of the website is open, but it is the kind of abstracted factory heavy Java where I couldn't figure out where it all happens. It doesn't happen in one place, but multiple abstract places and at some point I just gave up trying to reverse engineer how it is done. The signatures I calculated never matched.