Font size for printouts and organizing print options

[Oscar Levin]

We got a suggestion at a workshop last week that I think is a great idea: allow the reader to change the font size before printing.  For students (or the instructor in this case) with low vision, being able to get a custom version with text they can read would be huge.

Not difficult to implement this (especially using the reader options already present).  I think also adding line spacing and maybe even font choice would be good.  

The thing I could use some help with is presentation.  The details element that currently hold "Additional printing options" is getting very full.  Should we switch to a modal that pops up for all of this?  That would actually make the logic for displaying the printouts a little easier to manage (we don't need to refresh the page on every toggle, only once after all settings are confirmed).  For someone testing these out though, it is more clicks (since the modal needs to be opened and closed, and you can't scroll to see the result when selecting options).  

Other suggestions for controls and their layout are very welcome.