A PPD file contains a description of the attributes and capabilities of a given printer, such as paper sizes supported, the printable area of the page, the number and names of input paper trays, optional features such as additional paper trays or duplex units, and so on, together with the printer-specific PostScript language commands necessary to use the features.
file defines a simple generic printer supporting A4, A3, US letter, and US legal paper sizes, and supporting manual feed. It defines conservative margins (1 inch all round), and the documents generated should be compatible with most PostScript printers. It is suitable for producing PostScript files when the destination printer is unknown, and may also be used if the appropriate PPD for the printer is not available.
However, for the best results, we recommend the use of the appropriate PPD for the printer. This allows you to specify which optional features (if any) have been installed on the printer, and ensures that the Print dialog provides access to appropriate printer capabilities such as multiple input trays and duplex printing. This also ensures that the CAPI uses the correct values for the printable areas of the page.