how can user save their form before submitting?

Is there a SAVE FORM button that we can put on the form for the user to save to their computer before submitting?

There are several ways to do that.

First of all, you can save input data in the session. Please, check the guide below for more information:

http://www.jotform.com/help/97-How-to-Save-Forms-to-Continue-Later

Alternatively, you can enable the "Auto Fill" feature of your form. At that situation, your input data will be saved in your browser cookie. You can see the following guide for more information:

http://www.jotform.com/help/227-How-to-Enable-Auto-Fill-Feature-Save-Form-Entries-to-Continue-Later

If you have any question or issues, please do not hesitate contacting us. We will be glad to assist you.