Advertising on the digital documents.

Fortune
“Adobe and Yahoo put online ads into documents…
…Yahoo is beginning to publicly test a new type of online advertising it hopes will prompt publishers of newspapers, magazines and newsletters to let readers freely access their digital archives. As part of a fledgling partnership the company is announcing today with Adobe Systems, Yahoo can now make its contextual text ads appear alongside Adobe PDF documents in a format similar to a search engine…”

In my opinion it will be good method to place Google Adsens ads on the digital documents and earn more money.