Where are the print spool files stored?

I have problems with my server and the printer connected via USP (Epson 1160) it seems to have files spooled somewhere that it tries to print every time I turn on the printer. Always the same document. I can see it in the control centre but not delete.

Does anybody know were such files would be stored? What they are called? Etc?

OS 10.4.6

Thanks