How to restore shared review comment back to PDF?

Shared review backups the comment in XML files. If I lose the comments, how can I restore the comments back to PDF? 

I try both import comment and import form data using the XML file, but nothing shows up. It seems only FDF or XFDF file works. Do I need to convert the XML file into FDF or XFDF? If yes, how? 

Thanks for the hep.