You need to pay $5 to export your BookWright creation as a high-resolution PDF. You can get low-resolution PDFs for free though. To get a high-res PDF, click "Upload" in the upper right corner and then go through the steps for ordering one PDF and zero hardcopies.
BookWright is a free software from Blurb (for Mac OSX and Windows) for laying out professional-looking books, magazines, and eBooks. It's much more user-friendly than InDesign or other layout/graphic design software. I've been using it for a side-project with the Kuwait Dive Team. I'm baffled by it's low "user's rating" in this comprehensive review and would highly recommend it.