See also the Wikipedia entry on False documentation 
A false document is a literary technique employed to create verisimilitude in a work of fiction. By inventing and inserting documents that appear to be factual, an author tries to create a sense of authenticity beyond the normal and expected suspension of disbelief for a work of art. The goal of a false document is to convince an audience that what is being presented is factual.
In practice, false-document effects can be achieved in many ways. Tactics have included the following: fake police reports, newspaper articles, bibliographical references, documentary footage, or using the legal names of performers or writers in a fictional context. Supplementary material such as badges, identity cards (IC), diaries, letters or artifacts can also be included, and this extends the exercise beyond the confines of the text.
False documents intentionally blur the boundaries between fiction and fact, and, in some cases, the difference between an artistic achievement and a convincing forgery is slight. Sometimes the false-document technique can be the subject of a work instead of the technique behind the work itself; however, these two approaches are not mutually exclusive, as many texts that engage "falseness" operate on both a literal and thematic level.
A false document is usually created as an artistic exercise, but occasionally is promoted in conjunction with a criminal enterprise, such as fraud, forgery, or a confidence game. A false document should not be confused with a mockumentary, which is a fictional film presented in the manner of a documentary.
A group of created documents:
- Literary forgery
- Codex Seraphinianus
- Dictionary of the Khazars - see the Wikipedia page 
- Dossiers Secrets d'Henri Lobineau
- Fictitious entry
- The Griffin and Sabine Trilogy - see the Wikipedia page 
- User:Keysanger/photo - see the Wikipedia page 
- The Report from Iron Mountain
- Thiotimoline - see the Wikipedia page 
- Salamander letter
- Tlön, Uqbar, Orbis Tertius - see the Wikipedia page 
- Villejuif leaflet
- The War of the Worlds (radio 1968) - see the Wikipedia page 
- The War of the Worlds (radio drama) - see the Wikipedia page 
It is not certain whether the Voynich Manuscript is a false or created document.
There are a number of webpages on 'false documents' in the legal sense.