first, make sure the latest version is checked in. Then clear your local cache to eliminate the possibility of the older drawing rebuilding with more recent version models. It's important that your cache is empty so that PDM can retrieve the correct version models, as it will not overwrite newer versions with older ones.
Use the "get" option to retrieve the old version of the drawing, and the model versions associated with that drawing version. Now Solidworks should be able to open the old drawing version as it was last saved.
if you just need to view the old version of a file, select the file and open its history. select the verion you want to view, and there is a view command (either on the top or right depending on your EPDM version).