Adobe has teamed up with Yahoo! to serve contextual ads on PDF files (see
link). I wonder why it took so long to do this? In the old model, pdf documents carried static ads that were created with the content as part of the page copy. In the new version, ads are dynamically matched to the content and displayed at view time by ad engines. In this three way dance between the publisher, Adobe and Yahoo!, everyone benefits. Publishers are able to bring more content by subsidizing them with ads, Adobe gets more revenue from its platform and Yahoo! gets to serve more ads to users. The users could potentially benefit the most by having access to more free content.