BUT, when I print, my left border is trimmed by at least 2mm (can't tell precisely how much). I have my 5mm white margin present but the image printed is truncated. Why does QImage show the proepr page layout, with the correct margins and then the final print doesn't match what I proofed?
This is a known HP driver quirk /bug.
Many have success by clicking on HELP in Qimage, and then RESET Printer settings. The driver settings are partially remembered and partially recalled.
Just Clear the diver, and set it all to teh correct paper, color management, etc, doing it manually.
Fred