The entire 7,000-page report on the U.S. handling of the Vietnam War is being handed out by the National Archives Presidential Libraries and Museums.
Prepared near the end of President Lyndon Johnson's term by the Defense Department and private analysts, the report was leaked primarily by one of them, Daniel Ellsberg, in a brash act of defiance that stands as one of the most dramatic episodes of whistleblowing in U.S. history.
Scholars aren't likely to find any great new revelations in the full report.
The Pentagon Papers showed several administrations had been escalating the Vietnam conflict while misleading congress and the public.
Ellsberg served with the Marines in Vietnam and came back disillusioned. A protege of Nixon adviser Henry Kissinger, who called the young man his most brilliant student, Ellsberg served the administration as an analyst tied to the Rand Corporation.
"I was part, on a middle level, of what is best described as conspiracy by the government to get us into war," Ellsberg said.
Johnson vowed in the 1964 presidential campaign that he sought no wider war, Ellsberg recalled, even as his administration manipulated South Vietnam into asking for U.S. combat troops and responded to phantom provocations from North Vietnam with stepped-up force.
"It couldn't have been a more dramatic fraud," Ellsberg said. "Everything the president said was false during the campaign."
His message to whistleblowers now: speak up sooner. "Don't do what I did. Don't wait until the bombs start falling."
The Associated Press contributed to this report.