I would hope that adobe is, at this point, sophisticated enough to break the shit out of their software once it detects that the registration key is compromised and being used for piracy activities. You might be able to find a torrent version that's had the registration module ripped out, but it won't be update-able, will probably be glitchy in strange ways, and almost certainly has malware on it that will make your computer part of a botnet, a click farm, or will simply try to steal your identity.
The only way you can really do it these days, is if you buy the software with a friend. The registration system probably has some leniency built in, so it won't hose your software if it only detects a couple installations. maybe.