How to combine two 1-page documents into two-sided print?

I have two 1-page documents and double-sided printer. I can print them separately but prefer to print them on two sides of one sheet. The documents have different formats and cannot be merged by their editor tools. Is there a technique to append one print page to another at printer level? There are PDF, XPS and print to file options which seems attracitve candidates for page shuffling. Edit 12 Nov 2015: I considered the mechanical alternative, where you print first surface, return the paper into the tray and print the second. But, I would like to avoid it because you need experimentation: you never know which side is printed first. This is aggravated by enterprise printers, which are located far away and used by other people as well. You can spoil their work if place you half-printed sheets at wrong side. I therefore ask for electronical merge/queuing.

Print the first one and then turn the paper round and print the second one seems to be the easiest solution.

Thanks, I considered that. But, we have enterprise printers that are located in distant rooms and you never know which is the surface that printer will print to (it may easily print on top of the first page, which needs experementation). So, I would prefer to combine it electronically and print.