[cups] New page for multi-document jobs in duplex print

[Marcel Schnirring]

Is there a way (option?) so that multi-document jobs add one empty page for
documents with an odd number of pages in duplex print (and multiple empty
pages for multiple pages per side option) so that each document start at a
new sheet of paper?

As far as I have understood cups, it should be in the filter for the
conversion to "application/vnd.cups-pdf" because backends no longer know of
the different documents.

Thanks,
Marcel