The Pentagon papers are the papers related to the political and military involvement of the United States in the Vietnam. They were prepared by the United Stated Department of Defense.
The impact was the people went to know that they were misled about the intentions of the government about their military actions against Vietnam. Kennedy extended war, despite his statements of stopping the war, everything became visible and public. These papers showed people that governments lie and this is the basis of the inability of the general public to develop trust in the government.