Software maker Adobe Systems Inc and Internet company Yahoo Inc said on Wednesday they will offer a service to let publishers run advertisements in Adobe's popular document-reading format.

The new service, Ads for Adobe PDF Powered by Yahoo, presents publishers with an alternative to conventional subscriptions, which, if widely adopted, could open up a new model based on free, ad-supported publishing, analysts said.

The deal is the latest move by Yahoo to expand the reach of its advertising beyond Yahoo-owned sites. Since last year, Yahoo has signed partnership deals to supply online ads to Web auctioneer eBay Inc, cable TV group Comcast Corp and a consortium of U.S. newspaper groups.

The Adobe service allows publishers to generate revenue by including text-based ads linked to the content of an Adobe PDF (portable document format) page in a separate side panel.

People want content for free, said Matt Swain, an analyst at market research firm InfoTrends, who has been briefed by the companies on their plans. The question is how do I reach consumers without charging them a subscription fee?

The service is set to begin public testing, which will run several months, the companies said. An earlier private test included technology and professional publishers IDG InfoWorld, Wired, Pearson Plc's Pearson Education, Meredith Corp and Reed Elsevier NV.

The free service requires no special software and is open to U.S. publishers of English-language content, initially.

Publishers who join Yahoo's online advertising network get access to the Web company's extensive network of advertisers.

This is powerful up and down the spectrum of publishers, said Todd Teresi, senior vice president of the Yahoo Publisher Network, of how customers could include everyone from media conglomerates to a school's parent-teacher group newsletter.

Advertisers gain a distribution channel that can reach highly specific audiences based on their reading interests while allowing them to track how specific ads perform. The approach is akin to how Web-based, pay-per-click ads now work.

Publishers who rely on Yahoo for corporate brand or Web-search advertising will have the option of delivering ads in PDF-based publications as well, he said.

From an advertiser point of view this looks like an extension of our existing marketplace, Teresi said.

The text-based ads are displayed in a panel adjacent to the content with no moving or flashing elements. Each time the PDF is viewed, ads are matched by Yahoo to the content.

In terms of relevance to advertisers, such ads could rank above Web-page banner ads in terms of targeting capacity, but below specific keyword-based Web ads, Teresi said.

An Adobe executive said the project remained in an experimental stage, part of a long-term market evolution.

Details are at

(Editing by Braden Reddall)