The idea was that out of the billions of PDF documents produced every year, some of them get passed around enough to warrant advertising, especially those produced by traditional print publishers. Adobe teamed up with Yahoo to provide contextual text ads similar to what you would find next to that document if you were reading it online. Hey, inventory is inventory, right?
In a note to program participants, Adobe fobs off the failure of the PDF ads on the economy and its need to focus on its core products. But it was simply a bad idea. Trying to turn PDF files into an advertising vehicle was just never going to fly.
First, who wants to click on ads in a document? It is an unnatural act. Second, unlike a Website where advertisers at least have some sense of who the audience is, PDFs get passed around and downloaded willy-nilly. There is no good way to track who receives them, or who ultimately might click on those ads. Incidentally, this download problem also plagues ads in videos—advertisers are more comfortable paying for the ads watched in a stream than ads bundled with a download. Third, if the content in your PDF is so compelling that you think you can run ads against it, you are better off turning it into a Webpage.
And that’s my problem with PDFs, I guess. Adobe has done everything it can to protect the format instead of making it easy to publish PDFs as full Webpages.