I agree PDF is not entirely useless. I don't mind it that much for papers, but I don't see how it's any better than responsive formats. It's obviously important for presentations where exact visual relationships between items is fixed, or flyers (things that inherently get published on dead trees—leaving layout to an html rendering engine in that case is not great), or other things like that.

I still don't understand why it needs to look exactly the same. I get that habitually people say "turn to page X and look 2/3 down the page for the line starting "The quick brown fox jumped", but with digital documents that's not in my experience how anything works. You just say "the sentence starting with 'The quick brown fox'", and everyone can search for it in a few seconds.

If an official proceeding needs to be sure everyone's working from the same document, they can distribute, or publish hashes of, an epub or mhtml the same as they can for a pdf. There's no assurance that two pdfs that you think are the same document are actually the same document, any more than two epubs would be.