When utilizing calls with the Windows ShellExecute API, using the "PRINT" or "PRINTTO" verbs results in incorrect application behavior based on Windows standards. Both should print without opening the application, but the app opens anyway. Changing the nShowCommand parameter seems to have no effect on the behavior. Interestingly, the files you print close but the app just decides to stay open.
Please correct this issue as it causes developers to have to go to all kinds of lengths to correct the problem.