

Meanwhile, I recommend you to follow the steps in the below article and check if it helps.

I appreciate you taking the time to share your concern and thank you for using this forum, it is a great place to find answers. Hoping someone will be able to help me on this. And of course I don't know if it will solve the problem.
HP DESKJET 9800 DRIVER FOR MAC HOW TO
But instructions given for Windows and I I can't find any instructions how to assign this driver under Mac OS. But someone on HP Support suggesed downloading Deskjet 9800 driver and assigning that to the 8600 printer as it has the necessary custom paper size capability. I found dozens of others frustrated with this same problem but no solution that clearly worked, at least for Mac users. But it seems custom paper size management is NOT a function of the 8600 model and none of the suggested workarounds I've found thus far have helped. I have latest Mac OS 10.12.6, latest Print Driver for the 8600, latest Avery Design Print software and have tried printing through Avery's online Design Print setup. Most important want to print Avery Mini-Sheets of File Folder Labels which is label # 2180, sized 4.25" X 10".

Hours and hours of frustration trying to find a way to print custom sizes of paper on my OJ Pro 8600 Premium / N911n.
