I'm currently writing a big document in LaTeX. The language is English and since I'm not a native English speaker, I've found a friend who will review and correct the document for me as soon as I have finished it.
Now I'm thinking about how this can be done. I don't want him to change the original version of my documents, since maybe I don't want to include all the modifications. So how can I best compare two different versions of LaTeX documents to see what he has changed?