This IBM doc describes the whole process.
Creating AFP Resources using IBM AFP Printer Drivers
You are basically using whatever pc product to take an image, print to a pc defines “AFP Printer” (which writes a pc file, then exporting that to the iSeries. iNav has the export process, or you can ftp it.
I can confirm the workability of IBM’s solution, mentioned below by Jfranz.
We use MS Word to create the overlay, then print to the IBM-supplied AFP printer on the PC, then exported the overlay to the iSeries. Finally, we specified the overlay in the print file. At this point you are good to go. No further overrides or anything is required. Just use the print file as you normally would.
One of the forms we converted is a sales invoice. Sometimes the form is printed, sometimes faxed to the user using the iSeries fax feature, and sometimes sent to the user attached to an e-mail as a PDF, again using applications on the iSeries. Everything happens on the iSeries.
One important difference in this technique compared to some of the other forms packages is that the data your applications prints has to be adjusted in your application instead of moving it around with the overlay application. After working with both methods we like having complete control of the printed output ourselves instead of relying on the forms application.
Good luck. It is not as compliated as it may first appear.