I often work with customers who are running the 64 bit version of MOSS, and they always want to know what the story with PDF support is. Yes, you can hack the Adobe 32 bit iFilter to work on your 64 bit farm, but it's probably not a good idea, as it's not completely supported. For those of you who don't know, there's a 3rd party company, FoxIT, who makes a 64 bit iFilter. It runs significantly faster than Adobe's 32 bit iFilter and its accuracy is better with expired documents. There's a posting on the iFilter blog with specifics.