Can I change an existing short-text field into a long-text field (without losing the data)?

The field I would like to change is "Price Includes" on page 5 of the form http://form.jotform.co/form/31775062889871

The current field is too small to enter the necessary amount of text. I cannot see an option to change the type of field to "Long Text".

Thanks

You can increase its width by going to Properties>OPTIONS>Width and change the value of the width.

But you want to make the Short Text Entry into multi-line, it can't be done. You need to use Long Text Entry.