Consulting Reply:
What we suggest for this process of negotiating and redlining is having the customer use the Comment button when they are reviewing the document to sign.  That will open the document up in Google Docs.  From there they can make “suggestions” to change the text or select text and make comments.  It is very intuitive.  You will be notified when comments/suggestions are made to your document.  And then the Sales rep can open the google doc and see those suggestions/comments and can reply back, reject them, accept them.  All versions are saved in google doc in revision history.  There is not downloading/saving, back and forth activity like with Word.  The goal is to do this suggestions/comment resolving back and forth and all the changes are in the document in real time.  Once everything is resolved the customer can then just sign the document with the same link as they see it with the current version/updated version.