Building on the literary history of word processing theme here's an interesting post from the Guardian
McCrum's major point is of course that due to the inherent revisability of wordprocessed documents we cannot necessarily follow an authors thought processes through drafts. This is of course not quite true, the dreaded 'track changes' can go someway towards this, even though what it produces is incredibly overloaded and impenetrable.
However the situation is even worse for historical archives. We may have 'track changes' set on and the documents correctly indexed and filed, but we are missing the marginal notes, the comments (and the postit notes and highlighting) that might reveal how a decision was arrived at.
We would only ever have the official version with the official revisions. Even in the days of typwritten memos we always had the marginal notes because of the expense in time and effort of creating revised versions.
Nowadays of course clean copies can be produced at the click of a mouse, and the scribbled annotated drafts end up in the big blue secure disposal bin ...