GtkPSproc is a front-end for the PSUTILS. PSUTILS is a set of little programs that allows to manage
in a lot of ways your PostScript files.
GtpPSproc is designed to work from all programs that uses CUPS (which are nearly the 100% of the GNU/Linux
programs), by emulating a printer (virtual printer), but it can work alone too.
GtkPSproc allows to adjust all the programs to your printer type (for example, sending always the
pages in reverse order), to group two or more pages in a sigle sheet, to print booklets, to easily
print in double-side fashion and to preview the work before sending it to the printer.
Maybe you can ask why use GtkPSproc instead of GtkPrint interface, having in mind that the later has
nearly the same capacities than the former. The answers are:
GtkPrint doesn't allow to print in bookled format.
GtkPrint doesn't emulate doble-side printing in single-side printers.
GtkPrint doesn't remember if it has to invert the page order for each configured printer.
There are still a lot of programs not ported to GtkPrint, but all programs can work with GtkPSproc.