Bottom of every print gets cut off

Hi. I am desperately trying to get my HP to print correctly - but every print from this computer has 1cm cut off from the bottom of the A4 page. The other margins are fine. If I try to adjust the margin say, in LibreOffice, it says it's outside the print area (it never has been on other machines!) If I print the ubuntu printer test page, it does not print to the bottom of the page either.

The printer is fully aligned and works fine with a Windows computer.

PLEASE HELP! This is stopping me from publishing my work.

Some info
OS: Ubuntu 14.04
Printer: HP deskjet 3050a j611 series

HPLIP: Have tried Ubuntu-native version, and latest install from your website. Problem persists with both.
Settings: All appear correct in HP device manager - paper dimensions are set correctly, but problem still persists.
Diagnose driver: doesn't detect any problems. This should be the correct driver, but the problem still persists.

Many Thanks
Jon