Adobe ACROBAT 3D Manual page 688

Saving separations as PostScript
Depending on the prepress software available, a service provider may be able to perform
such prepress activities as trapping, imposition, separating, and OPI replacement at the
output device's RIP. Therefore, your service provider may prefer to receive a composite
PostScript file of the document optimized for in-RIP separations rather than a
preseparated PostScript file.
Saving the file as PostScript saves the separation settings, the PPD information, and any
color conversions you have specified in the Advanced Print Setup dialog box.
For best results, use the Save As command rather than the Print To File option available in
the Print dialog box. (See Conversion options for PostScript or Encapsulated PostScript
(EPS).)