VERIFIED SOLUTION i
If a customer is using Designer 6, they will need to add a new output device that represents the PS file output by choosing Data Stream type as Postscript and choosing other details.
After this, they will get an option to create output in PS in the production jobs.
Output devices created in a strand are not available outside it, so the production job has to be in the same strand to use this output device.
Doc1 Designer Series 6
UPDATED: November 8, 2017