Adobe’s PDF innovation has been nothing but giant frog leaps: online collaboration, interactive PDFs, rich multimedia, and complex 3D PDFs. And just when you think the PDF can’t get any better or leap any further, Adobe pushes the envelope once again.

Just yesterday, Adobe brought the PDF to yet another level with the announcement of their latest ad-enabling beta web service. Here’s a short summary:

Ads for Adobe PDF Powered by Yahoo is a limited online service that lets publishers generate ad revenue from within the PDF files they distribute using a pay-per-click model where the PDF publisher gets paid for every ad click-through done by the user.

As the title suggests, the service is powered by Yahoo’s inventory of online ads and network of ad partners. Participating publishers simply upload and register their PDF files to the service site .

Adobe then analyzes and reviews the file according to key words and context so that the files are enabled with dynamic and automated ads that are relevant to the PDF’s content. The PDF is then sent back to the publisher to distribute.

Where a minimum amount of disruption is the aim of the game, as is the case with reading PDFs, the ads will appear in a neat little side bar within in the PDF file itself. When you click on an ad a different browser window will open to display the web page, keeping your reading space clutter-free.

The service is free and currently limited to U.S. publishers and English content. Registration is required.

It’s become obvious that the PDF is not just a format that preserves and presents information anymore. Among other things, it’s now a useful marketing tool as well.

What else will it be able to do in the future? Will there be nothing the PDF can’t do? The best way to find out: stay tuned.

In the meantime, keep an eye out for those ad-enabled PDFs.