You can use the SolidWorks Compare Documents command to compare files in a vault or to compare a vault file with a file outside the vault.
See SolidWorks Help: SolidWorks Utilities: Compare Documents.
In SolidWorks CommandManager, click Office Products > SolidWorks Office > SolidWorks Utilities.
Click Compare Documents.
Under Version 1 and Version 2, select the versions to compare.
The selected versions open in separate windows.
Use the tools in the Compare Documents pane to complete the comparison.