In-Universe Marketing

A particular form of Viral Marketing.

You have a science fiction movie coming out. What can do you do to promote it that goes that extra mile?

You do In-Universe Marketing. You post "found" documents from within the universe. A "NBS Nightly News" broadcast from 1972 in your world? Great. Advertising a drink from your setting? Yup. Showing a half hour of dull security camera footage with maybe thirty seconds of profoundly disturbing stuff going on? Perfect. The diary of one of the characters, with pages torn out? Synergylicious!

Websites that use In-Universe Marketing are usually Logging Onto the Fourth Wall.

Supertrope to Alternate Reality Game (in that there is no 'game' in most In-Universe Marketing, per se; rather, all there is is the advertising).

Not all Viral Marketing qualifies as In-Universe Marketing; the product being advertised must be fictional, and the "found" document must be set in said universe.

(Debatable... and the debate is taking place here.)