Office-jet (as most inkjets) don't understand postscript - you have to go over Turboprint. First you may check Turboprint-drivers. Maybe one of the older Deskjet-drivers will work (If not I suggest to buy a postscript capable Laserprinter)

To print postsciptfiles from a application, you have install Ghostscript correct and to prepare Turboprint (prefs/printer)

44752535fd.jpg

Now you can send your postcript-output to logical device PS: , which is created from Turboprint during runtime. TP (Ghostsript) converts it to bitmap and prints it out to your printer (hopefully).

A hint: MorphOS does'nt have much drivers for such printers, and even, they are not the newest. So it makes much more sense, to user printers, which understand PCL or better, Postscript directly. GDI-Printers won't work!
A good coice are most of HP-Laserprinters. With .ppd-configfile (used by prefs/printers) and Webinterface they can adjusted fine. Even duplex will work.