The Pentagon Papers told the true story of what happened in Vietnam and what decisions were made and why. They also shows that the United States officials had lied about Vietnam. The papers themselves did not DO anything to Vietnam, rather they explained what had been done in Vietnam and they also showed that Johnson had planned on expanding the war in Vietnam, not ending it as he had indicated publicly.
The Pentagon Papers were mostly an indictment of the Democratic administration of Lyndon B. Johnson, but they fed the Nixon administration's preoccupation with finding information and document leakers. They eventually led to the secret White House "Plumbers" group and then to Watergate. In its turn, Watergate led to the first resignation of an American president, Richard M. Nixon. The Pentagon Papers contained plans to invade Vietnam, even though President Johnson had told the public that he had no intention to stage an invasion.
What the release of these papers served to do was to lessen popular support for the Vietnam war and to call the words of politicians into question.
In response to your question, then, with regard to what happened with Vietnam, the main element of the Pentagon Papers is the lies that were being told about US involvement in Vietnam and US intentions as to the future of the war with Vietnam.