DRM? What DRM?
This is not the result of any DRM removal process, as they only appear on books by one particular author - David Eddings. I suspect you are right and they were converted from fixed layout PDF's.
So far all his books that I own (I've got the lot except for Regina's Song) have an absolutely stupendus amount of OCR errors: missing full stops, missing commas, inconsistant use of dashes, spelling errors, new lines being created mid-sentence, paragraphs merging together, etc.
I've been making notes on my T1 for each issue as I come across them, but unfortunately my T1 has told me that I can't create any more notes as it's out of memory for them. Not good as I'm only about a 100 pages into the book.