It might make sense to use system services on a Mac to add the text to iTunes as a spoken track. Then sync with your iPad to get the tracks onto the iPad. Then you could rewind or fast forward the track as you wish just like any music track. You should be able to select all the text from the PDF then use the menu option
Preview --> Services --> Add to iTunes as a Spoken Track
Thank you for reading my problem and writing back. But this is actually not helpful at all.
If I told you my 2008 Subaru was not starting, you would not tell me to just use my 1984 Jeep. iTunes is the Jeep in this analogy.
Putting text to speech into iTunes is an ugly and awful thing. The voices are worse than the ones on voiceover. And users cannot control the speech rate. It would take me thousands of extra hours to read my law books using the iTunes feature.
I need to use VoiceOver. Or a text to speech program on PC.