Since **f** is singular (referring to one chapter or section) while **ff** is plural (referring to multiple pages), you could try **folio** for the former and **folios** for the latter. But it would be easier for the listener if you would say "Section/Chapter beginning on page [whatever]" for the former and "Page [whatever] and following" for the latter.
Think of it by analogy with **e.g.** :
* Saying the letters "f" and "ff" would be like spelling out "e.g."
* Saying "folio" and "folios" would be like saying "exempli gratia"
* Saying "Section/Chapter beginning on page [whatever]" and "Page [whatever] and following" would be like saying "for example."
Either of the first two would be odd and confusing. The last is what the listener of the audiobook would expect. After all, **f** and **ff** , like "e.g.," are typographical conventions, not representations of the sound of words.