Only because I'm rusty on the batch processing language, I'd be inclined to generate a file listing, then open the file in Word and use a wildcard Find/Replace, where:
Find = (<[A-Z0-9]@>)(.pdf)
Replace = REN \1\2 ^34\1 - Calculations\2^34
Then save the file and run it as a batch file.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]