'Set Download status to Not Downloaded' moves both statuses together and was the only
way to reset a PDF, so a user who wanted a PDF re-fetched also queued the audiobook
for a fresh download - which then rewrote that title's other files. Reported in
issue #1947.
Add a PDF-only pair beside it, shown only for a selection that has a PDF, since for
anything else the existing pair is already audio-only.
Co-authored-by: rmcrackan <rmcrackan@gmail.com>