Many times, companies like to choose whatever fonts that look good for paper hand outs or mailers. They do not establish a consistent look throughout the publications. However, it is highly paramount to choose a font and stick with it. If you start to establish that and implement the concept into all of your outgoing advertisements, the look of your company will start to become established.
Advertisements will start to become recognizable because you have stuck with a specific branding for the majority of your outside look. It is even helpful to nail down a document that writes down specifically how each form of mailers or print material will be formed.
Your logo is also key to establish your look. Picking fonts that compliment your logo will establish wonderful print media and allow for the look of each stand alone piece to work well visually.