The platform's Print Friendly option can be used to print most pages within the instance. This option is particularly useful to ensure that the page being printed is in proper print format. One of the options that would be useful is to change the font size of this print page. However, this isn't possible as the print friendly feature is non-modifiable. Instead the browser's print scaling feature can be used to adjust the font size.
Since it's not possible to change the font size of the Print Friendly page the browser's print scaling feature can be used to adjust the font size instead.
For Google Chrome browser at least this option can be found when "More settings" is toggled on the Print Preview window.