Lexmark s605 Printer: Printed output wrong size

I have just installed a Lexmark s605 printer as a wireless printer, on a home network using Lexmark driver from their website. The installation went smoothly, no errors, everything looks fine but when I print the output is very small, at least 75% smaller an 90deg rotated. All the obvious settings look fine, I’ve checked cups as far as I can because it is rather complicated for me, so has anyone got any ideas. (ps it prints fine from windows).