During SXSW Interactive, StumbleUpon launched a new advertising platform called Paid Discovery.

StumbleUpon says Paid Discovery delivers “an engaged target audience directly” to advertisers without clicking through ads or links. “100% engagement, 100% of the time.”

There are three versions of Paid Discovery: Light, Standard, and Premium. Light costs 5 cents per visitor, and is targeted by interest, location, and demographics. It includes basic reporting, and integration with Google Analytics.

Standard costs 10 cents per “engaged visitor”. It consists of priority serving in content streams, the ability to target by interest, location, and demographics, as well as by device (web/mobile), reporting that includes site performance and visitor data, traffic analysis, and website quality score, and Google Analytics integration.

Finally, Premium gets guaranteed top serving priority in content streams, standard campaign targeting options, advanced reporting, integration with Google Analytics, and costs 25 cents per “engaged visitor”.

“Millions of influencers are using StumbleUpon to discover the best of the web and mobile,” the company says. “By hitting a button in their browsers or on their mobile device, StumbleUpon users are directed through a stream of sites that reflect their interests and that have been recommended by friends.”

StumbleUpon is in a unique position to offer interesting advertisements, given the very nature of its service – discovery. It’s up to the advertisers, however, to create ads that are engaging enough to keep audiences happy.

StumbleUpon also launched a new iPhone app at SXSW.