[BetterRed]

Have you tried the Mammoth HTML->DOCX converter, either direct or via DiapDealer's DOCXImport wrapper plugin for Sigil; it provides the wherewithal to map Word's Style definitions to CSS definitions, but not much use if the DOCX is full of in-line styles

Or have you tried opening the PDF in Word itself. I am often pleasantly surprised at the quality of the DOCX it (Word 16) creates. That is, the DOCX will have a set of sensible Styles.

BR