The agent you’re trying to run is on the server. But, printing occurs at the client level. You will have to create an agent that the user will have to run (button, action menu, right-click) to print the document(s). You can use the following for the user to just print the document without being prompted for anything:
Printing can only be done from the UI (that is a client with a UI must be running). @Commands cannot be done from scheduled agents.
After saying that, there are ways to do almost anything. You might find some C API means of forcing a client to launch or mimic launching a client. Alternately, you could cause it to be opened in a browser or alternate client and print from there. I’m not saying I know how to do it, but there must be a way.