The Majestic Documents refers to several batches of allegedly leaked documents that pertain to a secret organization that is in charge of the UFO cover-up.
On 11 December 1984, Jaime Shandera, a producer of video documentaries received an envelope with a film of undeveloped photos. He met with Bill Moore who developed the photos. They contacted Stanton Friedman and sent him copy of the photos. For the next two years, they tried to verify the authenticity of the photos.
The photos were of several documents, which would later become known as the Majestic Documents or the MJ-12 Documents. They contained "an eight-page briefing paper to President Eisenhower detailing a UFO crash at Roswell, New Mexico in 1947, another crash at El Indio, Texas in 1950, and listing the members of the government's special Majestic-12 or "MJ-12" UFO group. It was dated "18 November, 1952", and it gave Admiral Roscoe H. Hillenkoetter as the briefing officer. There wasalso a memo from President Harry S Truman to Secretary of Defense Forrestal that authorized the creation of the MJ-12 group." (UFO Evidence / about.com)
One year later, Bill Moore received a post card with a cryptic message, which Stanton Friedman could explain. The card referred to a series of documents, kept at the National Archive in Suitland, Maryland, which were being declassified. Moore and Shandera went to the archive and "found a memo dated 7/14/54 from Robert Cutler, who was special assistant to President Eisenhower, to General Nathan Twining. The memo stated: 'The President has decided that the MJ-12/SSP briefing should take place during the already scheduled White House meeting of July 16 rather than following it as previously intended.' The memo seemed to provide independent verification of the existence of the MJ-12 Group.
In late 1992, three more Majestic documents appeared, this time received by a California UFO investigator named Tim Cooper. Cooper also received more documents in 1993, which Stanton Friedman investigated.
Finally, in March of 1994, yet another roll of 35mm film appeared. This time delivered to Don Berliner, Friedman's co-author on Crash at Corona. This one is part of a handbook detailing how to handle recovered debris and bodies from a UFO crash and is called The MJ-12 Operations Manual. Berliner turned it over to the General Accounting Office for investigation." (UFO evidence)
The original researchers who were involved are all mentioned above.
For a list of the alleged 12 original members of MJ-12, see MJ-12.
An introduction and overview of the majestic documents, complete with an assessment of the authenticity and copy of the documents can be found at the Majestic Documents website, https://majesticdocuments.com/documents/
The authenticity of the documented is disputed. Researchers like Stanton Friedman and Timothy Good doubt the documents are authentic but agree that much of the content is. They suspect several of these documents may be collages with passages from existing documents that were then photocopied together to make it look as if they were the original documents. Others, like Robert and Ryan Wood believe at least some of the documents are likely genuine.