Download the files file align.ps and alignmargins, then run alignmargins as root and follow the instructions:
Today I browsed along and across the linuxprinting.org, I downloaded all I could. Nothing worked!
align margins doesn't affect the margins, at least, in my case.
The print quality is cool, it's just unusable because of the margins
MDK 9.1; CUPS 1.1.19, HP DeskJet 9650 (Foomatic+hpijs); PostScript level 3.
PPD files for DeskJet 9600 downloaded from linuxprinting. I also tried to use my own CUPS-O-Matic PPDs with the same results.
On a landscape A3 print the picture is moved down and left.
On a portrait A3 print the picture is moved left and up.
Linuxprinting.org forums look nice, but, I fear, there are too many people having the same or similar questions... I found no hints.
Oh, what a hell the margins are!