Globally formatting OpenOffice labels

To easily globally format labels, you can either modify the Default style or select the Synchronize checkbox in...

the third tab of the Labels window. When you modify the Default style, just choose Format > Styles and Formatting. Find the Default style in the window that appears, right-click, and choose Modify, in the styles window, make the changes you want and click OK. All label content will reflect the change.

With Synchronize, a small button appears when you create the label document. Make the formatting changes you want in the upper left lable, then click Synchronize and the other labels will reflect those changes.