Hi Tim,
Please let us know the SAP_BASIS version + package level, and kernel version and patch level.
Have you tried to record an HTTP trace (with Fiddler or HttpWatch)? Usually you should be able to find a PDF file inside the trace (with Fiddler, you can analyze all the trace; with HttpWatch, only if you have the Professional edition installed). I would like for the entry where the printing service (BSP application) is called and see whether the issue happens after its call.
Regards,
Cris