You need Adobe Professional to do the form editing.

Once you have that installed, Go to 'Advanced' menu and select Form-->Edit fillable forms. You can then either enlarge the fill box size or reduce the fill text font size.

If you have filled the form already, make sure you save the filled contents and later import that data into your new form. The menu item is File->Form Data then select either export or import form data.

Adobe Professional is not a freeware so you may need to purchase a copy or try to find a evaluation copy somewhere on the web.