For me it is still not working, because I changed
/etc/cups/cups-pdf.conf
from
Out ${HOME}/Transport
to
Out ${HOME}
and get the error message
audit[5146]: AVC apparmor="DENIED" operation="mknod"
profile="/usr/lib/cups/backend/cups-pdf" name="/home/rudi/home_rudi.pdf"
pid=5146 comm="gs" requested_mask="c" denied_mask="c" fsuid=1000 ouid=1000