Can you explain bit further? Do you want to get a pdf of already printed or generated report which set for the default printer or do you need to generate a new report when changing the shipment status?
I have an existing shipment report (name :Dispatch_rep) .I want to get a pdf(Dispatch_rep) already printed to the default printer . when the shipment status is Closed.
In your case we may have to save the result key value of the printed report in shipment window or some where else, using a custom or customized field. Then we can re-view that report from report archive in the moment of closing the shipment. That’s the solution I can think of.