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I need to be able to use FDF's in PDF's and to do so I need to use Adobe Acrobat as Firefox's built-in PDF viewer doesn't FDF's. Problem is... that option is no longer appearing. "Use Adobe Acrobat (default)" appears as an option but not "Use Adobe Acrobat (in Firefox)".

Any ideas?

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Could you please confirm that Adobe Reader is installed in your PC and you've updated Firefox latest version!

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