You are viewing Windchill (PDMLink??) as an application, which it isn't. It is a platform that supports almost any activity you can imagine.
It's a continuum. Notepad is on the application end, the Internet is entirely platform. I place Windchill much closer to Internet than to Notepad. The non-Windchill Intralink is more of an application. It's software to use, not build a company operation on.
Depending on how skillful one is Windchill can be anything from entirely useless to practically magic.