In all of the scenes depicting President Nixon on the phone in the Oval Office, Nixon's actual voice is heard from White House tapes.
In his memoir, Daniel Ellsberg claimed that walking out of RAND with the Pentagon Papers (and returning them) over the course of months was a calculated risk, since he had never had his bag checked by security, but he did not know for sure if it was not policy to do so.
In scenes involving the Pentagon Papers, Daniel Ellsberg's original documents were used as props, including the pages that were scattered over the floor of Ben Bradlee's home.
Tom Hanks is an aficionado and collector of vintage typewriters, and he tried out every one of the typewriters in the Post's newsroom during the shoot and took one of them, a Corona Zephyr, for his own collection. 'I tested every single one of those machines and I picked out the one for me," he said. "I informed the prop department, I'm either buying it or stealing it - it's up to them."
Daniel Ellsberg lent his name to a paradox in decision sciences that he popularized. Termed the Ellsberg paradox, it demonstrates that human beings have an aversion to ambiguity and prefer a known devil to an unknown angel thus violating certain assumptions of rational decision making theory.