I'm not entirely sure on the specifics of what is allowed, but I know MathXL/MyMathLab has a button for printing when one is reading the textbook online through their site.
Oh god, MyMathLab. The second shittiest piece of software I was ever forced to buy. And at $120, it may have been the lowest value/dollar of any software I've ever interacted with.
Shout out to all the professors who either A) don't use textbooks, and only use free online resources or B) don't make us buy the textbook's shitty online service, so we can just go out and rent/borrow the textbooks for cheap.
Printing ? But that would mean circumventing DRM to produce an illicit copy - surely an honest student would not do that !