> Eyes only documents are old hat and are being destroyed as we speak.

Then I fear for the long-term record, as well as short-term security. Hard copy is still signed for wills, house deeds, treaties etc, for long-term durability. For the really long term, follow the example of the English Parliament: Hansard is still printed on vellum, because it lasts longer than even acid-free paper.

One of the fundamental problems with securing soft-copy documents is that, when you make a copy, the original is untouched. One can steal a hard-copy document, but its theft is easier to detect, because it isn't where it should be.