Every publisher has an approved list of fonts that they can use in their directories. If you are laying out your ad, make sure you are using only fonts that are approved for the directory you're advertising in.
Ignoring this advice can have a detrimental effect on your ad. Either the publisher will be forced to use your ad in a format that is less than optimal, they may exchange your fonts for approved ones that are close in appearance, or they may reject your ad causing a delay, frustration and more work.
Your YP sales rep will be able to provide you with an approved list of fonts simply by asking. Your ad designer will be able to get a digital copy of those fonts if there is any question about their compatibility.