How do I change the tabbing order on my PDF form?

I have created a registration form and saved it as a PDF.  However when I open the PDF and start filling it in I find that as a tab from one field to the next it is jumping around all over the form.  The form cannot therefore be filled in logically using the tab.  How can I change the order of fields so that the tabbing will lead the user through the form in a sensible way?

Hi! 

Tabbing will follow the order fields were created at. Looks like you have moved fields after they were created on your form. I can suggest to delete the fields and re-create them in order you would like tabbing to work. Please see: