You could take a class in desktop publishing but if you want to learn it on the cheap and having a certificate is not that important, I've got all the basics for you right here.
Discover the best desktop publishing software -- no matter what you want to create -- and the best techniques for creating cards, newsletters, logos, brochures, signs, and anything else that desktop publishing can create. Whether you have a lot of time or just a little, pick one of these self-paced paths to learning desktop publishing:
Crash Course for Non-Designers:
Crash Course for Designers:
Dig deeper, much deeper: Basic Guidelines and Requirements for Doing Desktop Publishing