Windchill is a higher level package - catering for more functions (purchasing, MRP, manufacturing, etc...) as well as engineering. It carries a range of interlinked information - parts, BOMs, documents, etc
Windchill runs on a web server - the clients run on browsers. It can take CAD data from Intralink (via a gateway).
Also - DesignDataManager is a Pro/E management package for smaller groups of Pro/E users. There are quite a few different PDM systems available...
Pro/INTRALINK is Pro/ENGINEER file management. It is a workgroup oriented system designed to manage the complex relationships between Pro/ENGINEER files. It has some higher-level capabilities like e-mail notifications and electronic sign-off, but it mostly resides in the engineering relm.
Windchill has been broken into Link solutions. Each link solves a specific enterprise wide problem. PDMLink is a web-based PDM system. It manages the products you design throughout their entire lifecycle. It overlaps Pro/INTRALINK with notification and sign-off. Then it goes way beyond with enterprise wide capabilites. You interface with it through your web browser, so anyone with web access and a login can use it. It includes ProductView for visualization. It can integrate with your MRP/ERP systems. Its functionality includes the ability to create and manage multiple BOMs for the various departments in a company. It even includes effectivity and document management.
PDMLink can handle Pro/ENGINEER files directly, but the current recommedation is to use Pro/INTRALINK and tie PDMLink into it. If simple vaulting is all you need, maybe PDMLink is the option for you. If you really need to manage your Pro/ENGINEER data, then use Pro/INTRALINK. If you need to manage your data and the rest of the enterprise needs to use it too, then both packages are the answer.
I can't speak to the other data management options available. The only thing I know about them is they cannot handle Pro/ENGINEER data as effectively or efficiently as Pro/INTRALINK. It has something to do with the APIs available to third party software development companies.