There is another way but it's a manual process and it's a HACK. Using this process will basically kill any XFA or JS functionality that was in the form previously. So proceed at your own risk...
Use a tool that can view and edit the internals of a "static" LiveCycle PDF form (i.e. Windjack's PDFCanOpener).
Delete the XFA dictionary
Do a SaveAs to a new form name.
Close the form
Re-open the form and then you should be able to edit the form with the Acroform tools.
Note: This WILL NOT work with dynamic forms.
Sabian