this is an issue in the legal world. court opinions accessed only online are cited according to their “page number” in some reporter or another. it’s better to cite paragraph numbers when possible but most American legal documents are un-numbered.
It sounds like the legal world can continue to use PDFs. That's fine!
Laws already have problems with HTML: numbered lists are specified in a way which is incompatible with many jurisdiction's numbering schemes, including the US Federal standard.