Probably not. I have not heard of any general/community library of UDFs going back to Rev 13 and when PTC User had only e-mail and there was no web interface for discussions; certainly predating PTC Community by a decade or more. PTC did sell "BASIC LIBRARY Catalog with UDF Library" as seen at cad.jhu.edu/doc/lib/basic.pdf and Pro/Engineer: Basic Library Catalog with UDF Library Release 18.0: Parametric Technology Corporation: Amazon.com: Books It included some shapes and a lot of screw threads as UDFs and a bunch of small hardware.
If you have a need for a particular kind then maybe someone has made something they could share. If so, then mention which version of software you are using. It is likely that UDFs can't be opened with older versions than the one they are created with.
As an aside to the Community, can UDFs be managed in a meaningful way in Windchill? I don't recall that UDFs are placed by reference so that they would be Check-in/out with an associated model and that they would be tracked as used-on relationships.
