Read the laws.
Presidents do not have to "declassify" docs, since they are above the laws on classified docs, can ignore the law on classified docs, and can do anything at all they want with classified docs.
{...
Security Clearances and Presidential Authority
By
Steven Aftergood • November 18, 2016
“Security clearances are not mandated for the President, Vice President, Members of Congress, Supreme Court Justices, or other constitutional officers,” a recent
Congressional Research Service report explains. “The criteria for election or appointment to these positions are specified in the U.S. Constitution, and except by constitutional amendment, no additional criteria (e.g., holding a security clearance) may be required.”
In fact, the security clearance system itself is an expression of presidential authority. Its scope and operation are defined in an executive order (
EO 12968), and its terms can be modified by the President at will.
And if the President wished to grant access to classified information to a family member, for example, there would be no legal barrier to doing so. See
“Trump Will Have Wide Latitude to Let Family Into Government’s Secret Circles” by Mark Landler,
New York Times, November 16.
...}