For anyone who read about Printopia and wished they could use it on Windows, I read about a program called FingerPrint today. It works similarly to Printopia, but has versions for both Windows PCs and Macs.
I think Printopia has a few more features, but it wouldn't surprise me if FingerPrint adds similar extras later.
I have not tested FingerPrint. I just read about it in MacWorld, so YMMV.