how to copy form data from one pdf to another?

Hi,

I have created a pdf, added form data to it. Saved the form data as a fdf file - all good.

I've updated the document and saved as a new pdf and would like to load the fdf data into it.

So I select tools - forms - more forms options, and press the "import" function  - it goes grey and nothing happens.

If I re-open the document the import function remains greyed out.

I can find no way to import this data.... any ideas?

I've tried going into form edit mode - adding a new field.  The import option is no longer greyed out so I click it and can select the fdf file hit open and ... the dialogue disappears and nothing happens.

Is my Acrobat XI 11.0.07 badly installed - or what?