I do not believe that there's any real way to confirm that it "actually" printed. Once PlanetPress sends the job to the printer, it no longer has any access to it. You can confirm that the job is generated, and sent to the printer, but what actually happens after that is out of control of PlanetPress. Closest thing I can think of is using the SNMP Condition to check if the printer is actually printing, but there's no way to be sure WHAT is printing. Could be the PlanetPress job, could be something else entirely...
This kind of information is more something that you'd find on the printer itself. Check if your printer has any ways to keep track of the number of jobs that prints, you may also be able to find how many printed, and how many errored out. Again, the flaw here is that the printer will keep track of ALL jobs, not just the PPress ones. So unless you have a dedicated printer for your PlanetPress application, this might not be reliable.