Okay, I thought I would post this here just in case it would help someone else in the future.
I had a document that I wanted to print double sided and then fold into a booklet. But every time I printed it, the back side was upside down.
My printer is an HP 8500.
Using previous printers, there would be an option for long-edge or short-edge binding - and that would fix it. But I couldn't find the option in the printer setup dialog for this printer.
The answer is: on the right side toward the top is an little image of a piece of paper - click on it and it changes between long-edge and short-edge! (It shows you which one is currently selected in the image.)