What Would Happen If a President with Access to Classified Documents Had a Eidetic Memory?

Presumably Trump had already seen the information contained in the classified documents he unlawfully held on to.

Now whether a short attention span dummy like Trump would have memorised any of it, or even read it to begin with, is another matter. But, hypothetically, what's to stop a POTUS with a perfect memory recall to memorise all the information contained in those documents long after they've left the White House? Of course, they couldn't rely on the docs for evidence when trading with malign forces (e.g. Putin) or try to sell them off, but they could still trade on the information contained in their head, on the basis that as a former POTUS they'd of course have seen that intel.