I'm certainly not an expert, but perhaps you could strip all the form fields and use Acrobat to automatically create all new form fields. This shouldn't take too lang if you have fewer than 50 or so fields, even if needing to match field names, etc. You would, of course, lose feautures associated with a Designer form.
You can do it but its quite a job and in a way it will be like designing the form twice. First, you will add and layout all your fields in Designer. Then once you are happy with the layout, you need to PRINT the form to PDF (Note: this is Print and not Save As). It will then be a flat page with no fields on it. Then you can open that flat PDF in Acrobat and then add the fields again where the old fields used to be. None of the Designer functionality will exist in this new form so you cant add scripts in designer and bring them into the Acroform. Scripts will need to be added in Acrobat itself.