ArcGIS desktop does not require large-format printers to be PostScript-enabled. However, some users may choose to purchase the PostScript version of a printer to gain more options and flexibility. This is because in general, the PostScript-enabled printer drivers have many more settings and features with regard to color correction, print quality, and job handling.
The background of PostScript printing is that the PostScript language was the original language used for most printing.
A more recent method in the printing industry for printing large print jobs is to use a software rasterizer, sometimes also called a raster image processor (RIP). The RIP is an application or hardware device that would handle the conversion of a large job from the application into the language of the printer, alleviating the need for the printer to contain large amounts of RAM and a hard drive for processing.
Printer manufacturers, especially large-format printers, have generally built product lines around the two printing methods mentioned above, releasing the same printer as two versions. The PostScript version usually includes an onboard PostScript rasterizer (hardware or software) for processing PostScript print files directly. The PostScript model usually costs more because of these added software components.
In the past, a RIP was a required part of the printing workflow for any large-format job. However, even without using a RIP, many modern 'stripped down' printer models can print the same kind of jobs that the more robust PostScript version models can by using the standard Windows printing method.
ESRI customers can choose either of the two types of printers, as ArcGIS Desktop 9.1+ includes a rasterizer engine called ArcPress, which is supported on most modern large-format printers.