Create new config options to optionally link to a generate PDF file that
is published at the same location as the html files.
Note that the preview will not be able to download the file since
the file is in a different location. The publishing job moves the PDF
file in the top-level directory.
Change-Id: I3ff74030195b6a85ff4e4e3b62f367aa78f85b0a
e974da0a35