On GTK+ and Motif, CAPI uses its own printer definition files to keep information about printers. These files contain a few configuration settings, and the name of the PPD file if applicable (see PPD files for information about PPD files). When a user saves a printer configuration, the system writes such file. Note that because the printer definition file contains the name of the PPD file, it must only be moved between machines with care: the PPD file must exist in the same path.
CAPI User Guide (Unix version) - 30 Aug 2011