Change default paper size in OpenOfficePosted: February 7, 2012
So, you want all your documents to be A4 by default, but OpenOffice.org Writer keeps creating them in the US Letter format.
One of the ways to change the default is like this.
Go to the application menu and click through:
Tools -> Options -> Language settings -> Languages -> Locale Setting.
Pick the locale of your choice.
Presumably it will give you the paper size commonly used in the particular country.