How do you tactfully inquire why a person wants your reprint? My boss is first author on several papers, and doesn't want to give a reprint to anyone unless he knows and approves the reason they want it. I know, I know. These reprint requests fall to me. How do I inquire why they want it, with an appearance of collegiality?

EDIT: By "reprint", I mean the PDF of a paper, requested from the author by someone who doesn't want to have to buy it at the journal website.
To the requester, you could say something like:


  For my records, may I ask why you are requesting a reprint? 


 Though, I think a good follow-up question to ask here would be "how do I tactfully tell my boss to field these reprint requests for themselves?" :^)