The Delayed in State notifications are cool but they don't necessarily go to a specific person. Usually, those are configured to a smaller subset of 'approver' users but not a specific person. The nice thing about PDM (that some people see as a drawback) is that file ownership can only be triggered ...

You can't really 'assign' a file to someone in PDM ... at least not as a 'out of the box function'.

However, I have created 'assigned to' variables on cards that can be updated for this purpose.