Hey there! Currently there is no way to send a document from SB Billing that will show the client the status of the plan, and how much is still owed. You could, however, take a screenshot and send that over. It would appear like this:
 

Since there is currently no way to do this other than to share the screenshot (which can be cropped), I recommend that you submit a feature suggestion. This is the 2nd time today that I had this kind of question. The more feature suggestions we get, the better!