TIL the most surefire way not to have sex is to buy a printer.
BTW - a terrible scenario instantly crossed my mind:
OP tells his friend he's not into her. Friend gets upset, friend eventually gets over it.
Time passes.
OP gets dumped by his girlfriend. OP suddenly realizes his printer-friend was somebody who wasn't overwhelmingly attractive but had spent time with, conversed and provided pleasant company for him for days upon days. OP suddenly becomes interested in his the printer-friend. Printer-girl doesn't reciprocate the feelings. Anguish ensues.
Also - turning someone down, regardless of gender, is hardly ever easy, clean and effective. Telling someone that they shouldn't be attracted to you, using even the most logical arguments, usually makes as much sense a writing a treatise on why someone SHOULD be attracted to you. "Well, gee - your conclusions seem to follow from the premises in a straightforward manner, I guess I'll love you now".
Lastly - there's this, seemingly off-the-wall saying that "Hell hath no fury like a woman scorned". In other words - she may get the picture, eventually... but once she does, you'll wish she hadn't. This does, of course, depend on the person in question and the extent of investment... but things can get pretty nasty, I'll say this much.