-8993 is not a particular PostScript error. It is a general error number Macintoshes used to indicate a communication problem between the Mac and the RIP. The number was only used in operating systems prior to OS X.
Solution
As far as I know, this error is usually caused by PrintMonitor, the little extension Macs use to print jobs in the background. Switching off ‘printing in background’ causes the error to disappear.