FinePrint (
http://fineprint.com/fp/) is at v6.25. Did you mean FineREADER ?
The yellow background doesn't matter, as long as the text is still legible. I came across quite a few scans of books highlighted in green, yellow and pink markers. Everything went better than expected, even with underlined text as long as it was in graphite pencil and not ballpoint pen or something else.
Quality trumps quantity every time. So my suggestion is to focus on quality and properly digitize them. Have you checked with Project Gutenberg yet? Google Books? Because chances are that many (if not all of them) belong to the public domain since their copyright probably expired decades ago. Some authors may not be alive today. Downloading them could save you
a lot of work.