Phaser 7500 won't print actual size

I have a Phaser 7500 DT and I'm having problems printing images at 100%. I have set up a image file in Photoshop and converted it to a PDF for printing. The image measures 214mm by 143mm.

In the Acrobat X Pro print dialogue it's set it to 'Actual Size' and within the Xerox Printer Driver it's set to 'No Scaling'. However the images prints at 314mm by 243mm.

Any suggestions on how to print at 100%?

Cheers

Simon