If you open your assembly and select file>save a copy, type your new assembly name, then a diolouge box will appear where next to each part there is a drop down box to select whether to reuse a part in the new assembly, or to rename the part in the new assembly. If you select rename, the default is that Pro E adds and underscore '_' to the end of the part name, but you can rename the parts here if you like. I use it if I have an assembly of parts but i want to have one part to have varying features in each assembly. I only have to create the assembly once, then, save a copy (reusing the parts that are common) but renaming the part I want to modify, so when I change this in the new assembly, it does not affect the similar part in the original assembly. I'm not sure if ProE will create new copies of the releted drawings using this technique though. Currently If you save a copy of a part, it will also save a copy of the releted drawing, which is useful. If you do it this way you would have to delete all the original parts if you don't want clutter.
