I use Microsoft Word 2007, which has the ability to export a file to PDF. I see above that Open Office, which is free, can do the same thing. I've been very impressed with what I've seen of Open Office, although I'm not quite ready to drop my Microsoft addiction.

Other formats were preferred in the past, but PDF seems to be the current favorite format that printers like to have for copy. It's all set up and fixed, so then the publisher can't blame the printer for layout mistakes.

-Joe-