Native to OS/400 IBM’s product is Infoprint Server which is a licensed program product albeit at a pretty reasonable price.
With iSeries Navigator ou can drag a spoolfile to the desktop (or another folder) and then open it in a PC application that would generate a PDF. I’m not too certain how any overlays, etc. would be handled with that option. Automating this process would take some work also.
Your best free bet might be to check some of the articles written on doing it other ways. Such as the following series from MC Pres Online. part adds functionality. Part One gives you a basic conversion utility and the additional parts add functionality.