Typically to revise a schematic you would export the schematic design (as a design XML, which can be archived) and re-import choosing a different name.
- Open the project (note all diagrams should be closed before running these steps)
- Select the original schematic design (Design1) > right mouse click in the project browser > export design
- File > Import > Import Design
- From this dialog you can rename the design (Design1_archive_rev_A)
Alternatively, you could just maintain the archived designs as XML - these can be stored on a vault.