Current we are using A4 for paper size so we need to change it to default for all profiles. There are tow places you need to change for this setting :
1. Change the Region Setting:
Go to System Preference -> Language & Text -> Region -> Select Australia.
2. Change the Paper size setting in Microsoft Office Word:
Open Microsoft Office Word -> Open new document -> Go to Format -> Document -> Page Setup -> Change Paper Size to A4 -> OK
Note: You can also do the same for the font setting default by following this instruction.