Jagged edge postscript/PDF file

Jagged edges of images can be the result of two separate problems:

(1)     You are not setting the proper options for print which may be downsampling and applying lossy compression your images. You much check all print options.

(2)     You are using transparency in your artwork and the images are involved with transparency, but the transparency settings are for too low a resolution.

Nonetheless, unless you are directly printing to a PostScript printer, there isn't very much good reason to produce PostScript. If you are trying to produce a PDF file, use the Save a Copy function and specify PDF, providing the appropriate settings for your needs.

Note that in general, the best printing from Illustrator is by saving as PDF using the PDF/X-4 settings and printing the resultant PDF from Adobe Acrobat (or Reader).

          - Dov

And why?

How are you creating the postscript file?