The ceremony also featured a moon rock 3.8 billion years old, collected by Mr Schmitt's Apollo 17 mission in 1972. He said the directive turns the focus of the nation's space program to "human exploration and discovery".
'We will establish a foundation for an eventual mission to Mars, and perhaps someday, to many worlds beyond'.
Space Policy Directive 1 says the NASA administrator should "lead an innovative and sustainable program of exploration with commercial and global partners to enable human expansion across the solar system and to bring back to Earth new knowledge and opportunities".
Space Policy Directive 1 makes official a recommendation approved by the NSC in October.
"You are ensuring Mr. President, that America will lead in space in the future and for generations to come", he added.
NASA recently announced that for human astronauts, the path to Mars will include a stop at the moon, where the agency may build a facility now being called the Deep Space Gateway.
"Today we pledge that he will not be the last, and I suspect we'll be finding other places to land in addition to the Moon", Mr Trump said.
In September, Trump nominated Representative Jim Bridenstine, a Republican from Oklahoma, to be the next NASA administrator.
SpaceX launches rockets for customers including Nasa, commercial satellite operators and the American military.
"Given its relative closeness, the moon in particular offers humans the best hope for long-term exploration and utilization", the statement said.
Pence said the order will "enhance our national security and our capacity to provide for the common defense of the people of the United States".
After the shuttle program ended, Nasa turned to private industry to fill in the gap.