How to create a new model from a comparison model

You didn't give any details of what you have tried or your system, such as using windchill pdmlink. So we will have to start with basic stuff. You can rename a part in windows but don't expect an existing assy to find it with the new name.

File - save as (if a part, it's just entering a new name, if assy, you will have to decide if you want new names for sub-levels or use existing)

File - save as save as backup (to copy an entire model with the same name to a different directory)

Using pdmlink, you can use the save as function from with pdmlink.