Do you have a subscription to Adobe's ExportPDF service? That is a requirement for this feature to work.
If you do have a subscription, make sure that you are logged in (if you see the blue "Sign in" at the top of the panel, you need to click on that link and sign in).
My experience is that it's much more reliable to go directly to the ExportPDF web site (http://exportpdf.adobe.com) and upload the PDF file to the web service without the help of Adobe Reader.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com