multi page pdf click problem

[7PastShilton]

Hi

file PDFS
equipment xerox nuvera
rip freeflow


we have to print a string of pdfs with multiple pages for each customer
so for example pdf 1 will contain a single page letter for one customer followed by a duplex 2 page letter followed by a 5 page letter etc

now we havethe problem if we just convert the pdf to run duplex all the pages are correctly printed abut we are charged click for ther blank pages

we normally get over this problem by converting the file to a optomised postscript and embed the instructions to turn on and off the duplex
this way the printer runs all the one sided letters as on click each and full speed

the problem i have is we are not allowed to change the file in any way so we have to pay full click and run the printer at half speed on all of our single pages

also we cannot change the order as the multipage pdf is pre mailsorted so we cannot break it down and resort 1st

we recive one file per day upto 10000 pages so you can imagine the extra cost

Any help would be greatly appreciated