I find that PDFLRF and soPDF work better than either PDFread (sorry Nick) or Rasterfarian for this job -- I'd recommend PDFLRF in particular for this job.
https://www.mobileread.com/forums/showthread.php?t=13135
I should say, Google already offers most of their public domain titles in both ePub and PDF format, though the ePubs are not that great.
Not sure why this thread isn't in the PDF forum.