Here are some links to instructions on creating a tri-fold brochure.

http://www.vtaide.com/gleanings/BrochureMSWord.htm
http://www.veradzn.com/home.html?gclid=CNKzw-as4qwCFQJ8hwodhHUIpQ (Graphic Design company for ideas!)
http://www.ehow.com/how_5817870_create-trifold-brochure-word.html
http://www.trickyways.com/2010/06/how-to-create-brochure-in-word-20072010/
http://www.word-2010.com/make-a-tri-fold-brochure/