I've done something similar for decades. I work in science, and need to cross-reference a lot. I have a simple scheme for that. When I refer to another page,

I've done something similar for decades. I work in science, and need to cross-reference a lot. I have a simple scheme for that. When I refer to another page, I write that page number in square brackets (in the text, and repeated in the outside margin). Reference to other books have the same, but the number is prefixed by an index number for the book, and then a colon. The page referred to also gets an entry added, in the same format but in angled brackets. This makes it really easy to propagate new information through my work. Apart from the possible addition of the angle-bracket entries, I never alter existing text. If I redo an analysis, I simply make a wholly new entry, and add an angle-bracket notation on the old entry. The square-bracket and angle-bracket scheme makes it pretty easy to update analyses, e.g. if instruments are discovered to be faulty on a certain date. In addition to this referencing scheme, I also have two-letter keywords for topic areas, and those go into the table of contents. Another difference is that my dates are written yyyy-mm-dd. A policy of photocopying new work every Friday afternoon is quite sensible. I don't keep the copies with the original work, though, out of fire/flood/etc concerns.