In November, Adobe and Yahoo partnered to create Ads for Adobe PDF. It's a free service that lets you earn money by placing ads in your PDF files. (The ads are text and are served from Yahoo! advertisers based on content.)
You simply upload your PDF and earn money based on inserted ads. (You do have the ability to block competitors.)
With more and more associations searching for ways to monetize Web content, this may be something useful for your association to explore.
You can apply to join the program here.
[ via Kevin Kelly ]