You should leave in the page numbers that existed in the print book for the reasons others have already listed, but it isn't necessary to fill in the page numbers that are not on the opposing pages if they didn't appear in the printed book. Strange things can happen, but usually when pages are missing from a scanned book they are missed in pairs, so knowing the page numbers of most of the pages arround the missing ones can tell you what is missing. People using Kurzweil and probably open book can always cause their program to use user defined page numbers starting with the first page with a number, and then checking to make sure the last page with a number still matches up, so they have correct page numbers throughout the book, and don't have to constantly look for numbers on preceding and following pages. Sarah Van Oosterwijck curious entity at earthlink dot net