Comment 6 for bug 345183

Ok, Thanks (dinky) for this information.

Till:
When you say:
"To let pdftopdf actually generate two copies do
PPD=/etc/cups/ppd/HP970Cxi.ppd /usr/lib/cups/filter/pdftopdf 1 1 1 2 "" eog-test-output.pdf > out.pdf"

If I understand that you try to set PPD while executing the filter, I think this does not works (at least for me):
paul@Arcturus:~$ TEST=56 echo $TEST

paul@Arcturus:~$

What works for me, is
paul@Arcturus:~$ TEST=56 ; echo $TEST
56
paul@Arcturus:~$

but then it is not temporary like I think you wanted.