Hmmm, not sure what you are asking here.
CUPS is probably handling your printer. If you put http://localhost:631
into your browser, you will be able to configure all sorts of things for your printer, including the default paper size (looks like you want it to be set to "Letter").
f your printer is already set for "Letter", but OO is defaulting to "A4", then you need to change something in OO. You can either do this with "Templates", or a quick hack is here:
Although this is an old post, and with my version of OO (1.1.3) the file to edit is now at:
Note that PPD_PageSize
is defined more than once in this file.
It is strange that OO does not seem to have an easier way to set the default paper size.
Hope this helps.