Is it possible for someone to save a form in progress?

Is it possible for someone to save a form in progress, so that they can come back to it later if they don't have all the information to hand when they first start filling in the form?

Yes, this is possible. We have two methods.

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

https://www.jotform.com/help/227-How-to-Enable-Auto-Fill-on-Forms

The save and continue by session URL allows your user to save and continue on another device and browsers while the autofill will enable users to save and continue on the same device/browser. 

We recommend the session URL method if the form will be filled by people who often switch devices.