Headings are found by type size and become real Heading 1, 2 and 3 —
what Word's navigation pane and table of contents read.
Tables keep their columns as tabs, so Word's Table ▸ Convert Text to
Table rebuilds them in one press. No cell is ever guessed at.
Repeating furniture is found by repetition: a line in the same place on
most pages belongs to the sheet of paper, not to the document.
Links are stored separately from the text in a PDF, which is why a
converter that only reads text returns a file where every link is dead. These become
real Word hyperlinks.
And why it cannot look identical: a PDF puts every glyph at a coordinate, while Word
reflows text as you type. What comes across has to be a paragraph rather than a
position — that is the trade for a file you can actually edit.