Thank you both for the answers. I would like to try the free Adobe PDF editor, but don't want to uninstall my paid Adobe pro version, so couldn't do that. I tried foxit, and chrome, but both would cut off the longer forms (Schd B p. 1 for example) at the bottom. Finally I just settled on Adobe pro and "Scale to fit" and I'll just hope the rather large margins and reduced-size forms are OK for IRS scanning.
