(B): I primarily use them to prep for sessions, and I refer to them onscreen. I also use my laptop to run the game, so I have all my PDF's for reference without having to print them out.
I do copy-n-paste when possible, especially for things like spells, feats or magic item descriptions that I'm putting in my PC or NPC character sheets. I'll print out the occasional page with a monster on it, but I'm more likely to input the monster into E-Tools so I can make stat blocks, or copy the picture into a seperate file so I can show the players a picture of what they're facing without having to cover up the monster name or stats (the WoTC art galleries are ideal for this, too).