Don't you see? Yes, the documents may indeed be trivial, unless you are a presidential historian or the curator of the Carter library.
But Williams admits that he is not one of the "rightful owners" of the document.
Where I come from, if you take something when you know you are not its rightful owner, that is called stealing. And it was a significant enough theft, in Williams' own mind, that by his own admission he was "perspiring heavily" at the prospect of being caught.
Of course it was stealing, but there are a whole lot of ways people steal that we are not going to prosecute. Padding an expense account or a mileage report a single bit, taking an extra fifteen minutes for lunch, coming home with a highlighter or ballpoint pen and it winds up in your desk drawer. Strolling through FR, when your boss is paying you to put in a full day's work. All of these would be a form of stealing.
Do you want to continue to freak out over something like this? If so, OIMC, your behavior is hysterical. You need heavy medication. Stop and VERY SLOWLY step away from your keyboard.