Can I add a button to let some save the data and complete it later.

The job application I have created is long because it just has to be.  Can I add a button or a way for someone filling it out to complete part of it and then return to complete the rest later.

 I saw something about people being able to come back and change data, and then it would send out an updated email.  I am guessing if something like that is possible.  I should be able to let them save the partially completed form and return later?

Yes, it is indeed possible, the method you have seen is the save and continue forms later, it uses a session variable which saves the data in our servers so it can be accessed with the proper link from any device, the data is saved when the back or next buttons are clicked, this is why a multiple pages form is required for this. 

To get more info about this feature, please check this guide: How-to-Save-Forms-and-Continue-Later

If you have any question, let us know.