No. No. No. NEVER scan loan docs at a Fedex Office or public library! The PC used to scan will retain a copy of the docs, which is a violation of NSA rules governing protection of client NPPI.
Pony up a hundred bucks for a portable scanner until you can afford a good multi-function machine.
Multi-function machines/scanners come with a software package that will translate your scans into .pdf format, which is the generally accepted program.
Using a phone app for more than 2 or 3 pages is annoying and time consuming. Get a portable scanner like Magic Wand to scan IDs without violating privacy rules by using your phone. Use a scanner with a good ADF (auto document feeder) to produce scan backs.
As with any business, this one requires an investment in the proper tools. A reliable vehicle, a good multi-function machine, a back up printer, a portable scanner, an encrypted email account... all should be as much a part of this job as your stamp and journal.