But that doesn't help. If I have in my hand what is supposedly a top-secret document then how do I confirm whether it's real or not? (Let's assume that the forgers haven't made any obvious mistakes.) I sure as hell can't go knocking on the door and asking whether I can compare this document with the original version.
A great example was the Rather-gate memos from the 2004 election, a supposedly "leaked" memo which got published with great fanfare despite the fact that the forgers did make some obvious errors (ie producing a 1970s document in Microsoft Word using default fonts, spacing and parameters). But if the forgers hadn't been complete dumbasses then how would we have ever known whether they were real?