Printer Margin Setting Problem

[Gerry Tool]

I have a Samsung ML-1750 laser printer which is installed using the
ML-1200 printer definition.  Installation created a ml1750.ppd file in
/etc/cups/ppd.

The upper and left margins are incorrect.  That corner of the page is
"off the page".  I have tried setting the margins in the printer
configuration tool and by direct editing of the imageable area for
Letter (which is the page size selected) in ml1750.ppd.

Neither of these causes any effect on the printed page as it comes from
Kate, even after restarting cups or rebooting.

What am I missing?

Thanks.

Gerry Tool