If you are starting on an even page number, are you expecting this to be printed on a single side and then all the other pages print double-sided?

I would really question why you don't merge the documents before printing - or print all to PDF and then join them there to output to a printer.

Otherwise you are going to need to fiddle with the last sheet of one file having to go back into the printer to become the back of the first side of the next print

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Andrew Lockton
Chrysalis Design, Melbourne Australia