If you are going to use PGP for non-commercial purposes, then you can simply use one of the freeware versions. But if you are planning to use PGP in a commercial environment, then you should purchase one of the commercial PGP variants.

Commercial PGP versions are now developed and sold by Network Associates, Inc. (formerly ViaCrypt and PGP Inc.). The GNU Privacy Guard can also be used for commercial purposes.

Where to buy PGP

If you are in...	...then go to
USA or Canada	http://store.mcafee.com/
Japan	http://www.pgpinternational.com/japan/
Rest of the world	http://www.pgpinternational.com/