Let’s say you want your students to practice past exam papers that you have in pdf format. Do you print them out and give a copy to each student or is there a way that uses less paper?
With Foxit Reader you can let your students write on the pdf file electronically. The same can not be done with Adobe Reader.

The text in blue was typed using the Typewriter Tool.
When the file is saved and opened again there are three lines at the top of every page that can be removed if you buy the Foxit Reader Pro Pack. Foxit Reader is free and the added lines don’t bother me for this use.