how to generate back annotation file (from PADS layout) to import in orcad schematic ??

Hi everyone,

i have the PADS layout file and Schematic in orcad(.dsn) file.i did auto renumbering (Ref des changes) ,that list should be implement in orcad schematic (back annotation).i could not synchronize pads layout in orcad file. is there any option to do the back annotation from pads layout to orcad schematic ??