Under print settings there are a number of options for print format (working, condensed, printout, printout grey, ...).
It seems clear that the print settings are configurable, but perhaps that is only possible programatically? I'd like to know to edit the print settings for a document, so the font size for the selected print setting is increased in size.
Under options inspector I did find Printing Environment, but don't see font options there. I also found global print options, and tried changing magnification:
from 1 to 1.5, but didn't see the effects of that when I did print preview.
A partial answer to this question is using Style:
This allowed me to increase the size of unreadably small output (both in the notebook and when it is printed). However, I'd still like to know how to magnify all the font sizes in the document when printing it, if this is possible, or set a minimum font size for all printed output.