Force setting standard paper A4

[oxy]

Hi,

every day I send a print job to the big printer, run 20m over the corredor
to read: "Insert us-letter". At ubuntu sys-settings it is A4, on /etc/cups
there is nothing about us-letter.

Why this print menu insists on us-letter as default?

Ubuntu: 12.04
OBS: off course i could every time change it by hand when sending
the job, but computers were thought to make life easier :-)