Additional filters can be added to the mime.convs file or (preferably) to other files in the CUPS configuration directory.
Each line in the mime.convs file is a comment, blank, or filter
line. Comment lines start with the # character. Filter lines specify
the source and destination MIME types along with a relative cost
associated with the filter and the filter to run:
super/type super/type cost filter application/postscript application/vnd.cups-raster 50 pstoraster