How to Change All Font Sizes in a Document at Once
http://www.taming-openoffice-org.com/writer/fontsize.htm

OpenOffice.org
2004

Abstract:

Many people want a facility in OOo to enlarge or reduce the size of all fonts in a document at once, preferably by clicking on an icon. Although I do not know any way to do that, I have found a workaround that provides a similar result. It takes a bit of setting up but otherwise works quickly and easily.