Step #1: Check out the file

Step #2: Do a get on the older version of the file you are trying to revert to. Make sure that it overrides the local copy.

Step #3: From your local drive, open the file. Do not open the file from Vault. Opening the file from Vault will download the most recent version.

Step #4: After opening the file, check in the file from its respective application. This will check in the older one to be the most recent version.