If you don't already have one, create a custom property for the revision level and populate it with the current rev level. Create an import workflow that uses the rev property as a filter to set the rev counter in epdm. It's a bit tedious to set up, but can be completed in about 20 minutes.
Look at solution S-09541 in the customer portal knowledgebase. This is for a one time mass update, not for repeated use.
To add to what others have stated...
"Our admin has explained all our revisions will revert back to 1/1 after migration and will need be dealt with one at a time
when a change occurs.
So, a drawing/model currently at revision C (for example), will migrate as revision 1. When this particular drawing/model
needs to be EO changed, the revision will have to be forced to D somehow."
There's more to the story here...this might be some confusion of Version versus Revision. Fairly accurate that any file added to the vault (whether via auto/manual migration or day-to-day use) will start at Version 1 (or there abouts, depending on add'l automatic processing)...but the Revision is a different story altogether.
The Revision scheme can be set to Alpha in EPDM as you currently have it in the wild (not sure why your admin would say it's "1/1"), and by using a Workflow as David suggests you can "fix" the Revision to match what your SW files' Properties contain. Or you can go the API route with a migration program that does essentially the same thing.
Of course, that's for SW files. Other CAD files (especially Pro/E) may require add'l handling to fix the correct Revisions (as well as patch up file references).
Actually SolidWorks drawings may require additional handling also. If you use model based properties - that your .slddrw templates are set up to borrow - that creates some extra issues. Because of the way the mapping works in this case (model to drawing to data card), the drawing data cards are not updated until the drawing is opened and saved in SolidWorks.
Sweeney - does your tool allow you to select multiple files from a search and run the SetRevision on all (if they all have the same rev level)? Does it work without changing state? """SetRevision optionally gives you the ability to automatically update the file’s data card all with the same command."" That means it will change both the EPDM revision stamp and our Revision variable on the data cards?
S-09541 was a good tip Dekoning, I wish our VAR had known about that.
As Marshall said, make sure you understand the different between Version and Revision in EPDM-speak. One other detail is that you can automatically transition all your files (for us it worked great with .sldasm and .sldprt, but not .slddrw, because of above mentioned issue) into the legacy workflow, so it will check their custom property revision letter and stamp that in EPDM. So even if you use the workflow it does not need to be "one at a time". That is one approach, but compared to S-09541 I'm not sure what is better.