I don't know about software designed specifically for doing this with legal documents but most of this you could probably do quite easily with some simple Unix

I don't know about software designed specifically for doing this with legal documents but most of this you could probably do quite easily with some simple Unix tools and a little scripting. I'm guessing the documents aren't plain text so the first step would be to extract the text. For example if they're pdf's you could use pdftotext. Then for: 1. diff/diff viewers like xxdiff(the name may have changed somewhat recently)/git 2. wc 3. diff with some scripts to automatically process the documents, count the number of words in the documents, and write to a csv file