This is a program I have not yet used, but it looks interesting. I had heard of it before but not looked into it, then a correspondent brought it up today. LyX is a free, program licensed under the GPL V2, and is available on all major platforms. Based on a quick look, it seems particularly suited to writing academic papers, and preparing them to be printed.
My correspondent, Morten Juhl-Johansen Zőlde-Fejér has produced a primer on this which you can read at http://writtenandread.net/lyx/. It looks interesting, check it out.