It would be great to be able to specify the font size for both the editor and the printed listing. Due to the high resolution on my system I use a font size of 14 to make editing easier (my eyes aren't as young as they once were), but that causes listings generated by File->Print to be excessively large.
Have you tried setting the font size to the desired size for printing and using File > Preferences > Interface scale to the desired size for on-screen readability? The interface scale option is a relatively recent addition so you will need to use a reasonably current version of the Arduino IDE to have that feature.
Interface scale causes both the print and screen fonts to scale by the percentage specified. I'm using the most recent version of the IDE, version 1.8.1.