To set the default paper size from Letter to A4 or Legal or other

To set or change the default paper size Letter to A4 or Legal or other size
(to printers).

For MS-Windows Users: 

1. Click on Start => Printers and Faxes
2. Locate your printer's name and right click on it and click "Printing Preferences"
3. Under the "Main" (General tab in some other printer models) Tab, and under "Paper Options" group, select the settings for "Paper Type" Paper Size". For paper size, choose A4 as you desire.
4. Click "Apply" and the click OK.
   

Your values here will be the default values loaded when you click the print command in any programs in your computer.

To set or change the default paper size Letter to A4 or Legal or other size

(to MS-Office-2003 Word Documents).

Path to trace Microsoft templates: (but the path is different to system to system):

C:\Documents and Settings\Administrator\Application Data\Microsoft\Templates

Save a word document with Naming "Normal.dot" (without Quotes), with your desired word document page set up (paper/margin). 

Then, all word documents open with your required page settings.
Note: It does not apply to MS-Office 2007 & 2010