How would I locate and mass delete over a thousand duplicate attachments

I’ve been brought into a laboratory group that has been busy for the last few years. They’ve amassed a shared EndNote library of over 3,000 entries. Nearly all of those entries have attached pdf files. Hundreds, perhaps up to a thousand of those entries may have duplicated pdf files. How do I do a database cleanup of these? I need to mass-locate and mass-delete the duplicate pdf files.
Let me be clear, I AM NOT ASKING HOW TO FIND DUPLICATE REFERENCES. This I can do, although the sneaky folks in the lab group have found so MANY ways to accidentally evade the duplicate reference detection, too…

I recently shelled out $12 for a program that does this for all duplicate files on a Mac, regardless of whether the files have different names. It was well worth it.

The one I used is called “Duplicate Finder and Remover” by Shrishail Rana. It does not collect personal information. There are lots of other, similar apps out there that have other specs.

So, EndNote can’t hack it and we have to resort to an external product. I doubt my department will pay for it.