A page must become a flowing document
PDF places words and images on fixed pages. HTML arranges content in a flow that changes with the screen. Conversion needs to identify paragraphs, headings, lists, and reading order; a visual page can contain objects positioned without semantic relationships.
Two-column pages, sidebars, and footnotes may become interleaved or separated in the HTML. Compare section order with the source and decide whether a clean responsive page requires editorial restructuring rather than a literal reconstruction.