Scribus
Scribus is a desktop publishing (DTP) application, released under the GNU General Public License as free software, with native versions available for Linux, Mac OS X, Microsoft Windows, and others.
Scribus is designed for layout, typesetting and to prepare files for professional quality image setting equipment. It can also create animated and interactive PDF presentations and forms. Example uses include writing small newspapers, brochures, newsletters, posters and books.
(adapted from http://en.wikipedia.org/wiki/Scribus)
To download, visit http://wiki.scribus.net/canvas/Download.