GIMP uses plugins for reading and writing all file formats except XCF. These plugins may use external libraries or programs. For example, GIMP does not directly support PDF and PostScript. Instead, for reading (or writing) PDF (file extension .pdf) and PostScript files (file extension .ps or .eps), GIMP requires a powerful free software program called Ghostscript.

Linux distributions almost always come with Ghostscript already installed (not necessarily the most recent version). On Windows Ghostscript[GHOSTSCRIPT] is included in the installer so you don't need to install it separately.