We too are having regular but intermittent problems with downloading PDFs.
In our case firstname.lastname@example.org sent us an email with a link to a PDF document on http://www.wipo.int.
Our PAs reported errors when trying to download it.
When I tried this morning at a variety of computers I succeeded once but all other attempts (including at the same computer) returned the error HTTP Error: 504 (gateway Timeout).
I take it this is a problem at the WIPO server, or is there anything we can do.