Isn´t scribus capable of including pdf files directly?
In my opinion this would be the better way - if it´s possible.
It is but my experience is that scribus seems to have more difficulties to use .pdf than .ps (I don't know why or even if it's not just with my version). pdf are imported as a standard image format , with a resolution etc...
I'm not a scribus expert so I'm maybe wrong, take it just as a personal feedback.
Matth
(PS : hope my english is comprehensible)