Oh, it's common in my country to use a smartphone to 'scan' documents by actually just taking a lousy photo of them. It's so prevalent that when you tell someone to do a scan they usually do this instead.

I bought a cheap canon scanner for 50$ and it's pretty perfect for legal documents. A little slow maybe. I use SANE, then do lossy compression too.

In rare situations I'd then post process the PDF to even worse quality using ghostscript, for example when a foreign visa application form requires a scan of a really long document, but doesn't accept sizes over 2MB.