I've googled this extensively, but there doesn't appear to be a common solution, or my keywords are inadequate.
We have a few large PDFs on the order of a few thousand pages each that describe some legacy software. Instead of searching constantly with Ctrl+F or keeping a directory of page numbers, I was wondering if there's some interactive tool that can allow us to tag text in the documents up front, and then filter with those same tags later to reduce a lot of the redundancy. It doesn't have to be specifically for PDFs, but it would be nice if it worked for those, Word documents, or at least plaintext. Without this, I think we're going to be wasting a couple of man-months on just digesting the legacy architecture.
If you have other ideas on managing this much documentation, I'd be grateful to hear them, thanks.