I recently refinanced my house, and realized that there was a potential for a LOT of this sort of thing. So I paid the app store a few dollars for a PDF modification program, and just put a shortcut to a scanned signature of mine, and added that in the right places. Requested the documents as email instead of fax, and emailed them back. Totally acceptable and saved a bunch of time (in waiting for the printer and scanner) and money (in paper and ink).