I am Sorry for delayed response.
Can you please state the Steps that you try to import?
Is the Issue appearing for all the PDF files?
Do you get to Import PDF Wizard ?
PDFs are supproted in Import process, so can you give us a Detailed Snapshot of the image.
See Item 22 at http://www.grainge.org/pages/authoring/rh8/using_rh8.htm
If that does not help, then provide Anjaneai with the information requested.
See www.grainge.org for RoboHelp and Authoring tips