Asking a celebrity Prof to sign a paper they wrote? So we are all fans of some professor at some stage of academia. 

If I see one in an upcoming conference/workshop, should I ask them to sign a paper that they wrote as it's also one of my favorite papers? (I'm sure I'm not the only one who brings a paper that someone else wrote when I know they will come for the conference/workshop).

How would you respond if you were the Prof asked to sign the paper?

Has anyone done the same before?
Just ask! In the past, before electronic publishing, one had to ask for physical reprints from authors. They usually signed them with a nice greeting, sometimes a signature, and occasionally nothing. I have sent reprints to other upon request and always with a signed greeting because I appreciate the request. I have a hard time seeing anyone being offended by it although an eyebrow may be raised by the request since it is now quite unusual. But it is a good way to strike up a conversation and contact the person. Personally I would try to approach the person away from an "audience" in order to not interrupt and have a real chance to state why you admire the work (person). I am sure some might say no but I would not be offended if someone asked me, not that I see it happening to me any-time soon.