PCMS is part of Design Extender. It hasn't been updated recently, so it may be a moot point.
To update you would have to probably create a new site in Dreamweaver and define CMS content. Then you could copy/paste the associated files that get placed on your site. I'd make sure to back-up your old files and database first since I'm not sure what version you have currently it might not be as smooth as it sounds.
This is something I could help with in a premier support ticket as well.