If they are checked in, and are linked to the SW part or assembly file, then they can be renamed like any other file in PDM without losing the link.
But to answer your other question, you could set up PDM to not allow duplicate file names for your CAD file extensions (slddrw, sldprt, sldasm)
Thanks for the reply Prasad. Forgive me if I'm wrong, but whenever we rename any file in the PDM, it always tells us it can't find it and we have to locate it manually. This is for .sldprt and .sldasm's, I'm not familar with the .cpt's or the .fld's. Will renaming corrupt the simulation project?
You can allow duplicate file names for specific extensions if you wish.
Go to the admin window and right click on File Types. Select Duplicate file name setting from the drop down. A new window will open. Select the third radio button and then scroll through the list of extensions. Remove that are OK to have duplicate names.