This is the exact right place for bug reports!

The problem was the software was detecting ".pdf.zip" as the file's extension, and then as a "safety" feature was shortening it down to a maximum length of ".pdf". There was no problem with the actual upload; just the filename it was referencing it as.

I've corrected the coding - so given a filename with multiple periods such as that in its name, the Wiki should now extract only the LAST one as the actual extension, and treat the rest as part of the main filename.