That's a non-trivial task. There are no such objects like tables, styles, lists or paragraphs in PDF so you would need to reconstruct this kind of information. Also, text and vector graphics is positioned absolutely. Tagged PDFs contains some meta-information about the document structure which could help but still it is a lot of work.

The fundamental problem is that PDF stores the document presentation while html defines the document and the presentation is created by the browser. And obviously, to restore a document definition from its presentation is hard as lot of information is missing.