We experience that the method IsCommonNameModifiable returns false, and the Common Name of the drawing cannot be set with the method SetCommonName, even if the drawing has not yet been uploaded to Windchill PDMLink and the config.pro option
let_proe_rename_pdm_objects is set to yes.
It seems to work for Assemblies and Parts, but not for drawings.
I am not sure if you have figured this out yet but I was experiencing the same problem and it turns out that you need to store the template file outside of PDM Link. For some reason if the drawing is created from a template that is retrieved from the data management tool you cannot change the PTC COMMON NAME even if it has never been uploaded. I began using a template outside of PDM Link and have had not issues setting the PTC COMMON NAME.