Create Booklet is a PDF service (and Automator action) by German developer Christoph Vogelbusch, which allows to create two-page booklets directly from the Print dialog of almost every OS X application. We have been granted permission to distribute it for free with iCalamus, so get yours right now!
To output your multi-page document as a PDF booklet, choose
File Menu > Print > PDF > Create Booklet in iCalamus. It will be created in seconds and opened in Preview, where you can optimize, print and save it.