Changing the Background PDF Form in a Filliable Acrobat Form

I have designed a Fillable Acrobat Form. For this i converted a word document into a PDF and then used that form and the Form Tools to create the PDF Form.

Now there is a need for some modification in the original word document and thus the resulting basic PDF form.

The basic structure of the form remains the same except for a few text modification and an additional page addition.

I need to preserve the work already done by somehow replacing the background PDF form with the revised form.

I dont know how to do this. I am using the Acrobat Professional.

regards

pramod, Mumbai.