Scribus, a free, open source desktop publishing application, offers a wide range of page layout features, but one thing it lacks is the ability to print booklets. Fortunately, I've come across a simple procedure that lets you work around this issue. Here's how to do it in Linux; Windows users should be able to follow along too.
First, you need to determine the size of the paper you're using and the size of the document you want to create. I'm in Europe, so I generated A5-sized booklets using A4 sheets. In the US, if you want to prepare a booklet with letter-sized sheets, you must set the Scribus document size to half the letter size -- in other words, 5 1/2 x 8 1/2 inches. In both cases, the orientation must be vertical.