Adobe's PDF (Portable Document Format) is one of the most popular ways to distribute printed information electronically.

But until now, there hasn't been an easy way for a business to earn money from the content it publishes in PDF form. All that's changed.

Ads for Adobe PDF powered by Yahoo service - announced late last year - lets you add pay-per-click (PPC) advertisements to your PDFs at the touch of a button. You earn money when readers click on an ad.

You may not make big bucks using this beta service, but it costs nothing for you to sign up and try it out.

Here are some tips for an effective PPC campaign.

Aimed at PDF Publishers

The new service is a logical extension of existing online advertising networks, such as those run by Yahoo and Google, which distribute PPC ads for Web pages.

With one of these networks, a business simply signs up for an account and then adds code provided by the network to its Web pages.

Ads for Adobe PDF

Ads for Adobe PDF lets you do the much same thing with PDF documents: After you sign up and submit your PDF for processing, the service places up to five ads supplied by Yahoo on a panel to the right of your document; the ads do not obscure the document's content in any way.

The service might be particularly valuable for a publisher that creates a significant quantity of PDF content such as articles, newsletters, and how-to guides. You can distribute PDFs either by posting them on a Web site or by e-mailing them.

Using Ads for Adobe PDF

During the beta period--which has no set termination date--a limited number of US-based publishers who apply for an account will be approved (Yahoo hasn't specified the exact number).