Recommendations for best software for splitting PDFs?
If I understand correctly, you already have large PDFs of your books and are just wanting to split them into individual song files?
If that's the case, and you're on a Mac- the built in Preview program works just fine. Put the pdf into "thumbnail" view, and then just drag the individual pages onto the desktop (or for multi-page scores, you can drag page 2 and up onto the thumbnail sidebar of your page 1- hope I'm making sense). I don't know PC programs, but surely someone here would.