Mac OS X 10.5 supports printing a maximum of 999 copies in a single job. To print additional copies, submit an additional print job.
Mac OS X 10.5: Printing more than 999 copies
When you print in Mac OS X 10.5, you may request up to 999 copies in the "Copies:" field. If you try to print a larger number of copies (such as 9999), this dialog appears: "Error printing."