Change the Font Size of PowerPoint 2007 Text
PowerPoint fonts are measured in points. The larger the point size of your PowerPoint text, the larger the letters. Text in a PowerPoint presentation should be no smaller than 28 points for people sitting in the back row of your audience to be able to read it.
Go to the Home tab and select the text you want to change. Then use one of these techniques to change font sizes:
Font Size drop-down list: Open this list and choose a point size.
Font Dialog Box: Click the Font group button to open the Font dialog box.
Increase Font Size and Decrease Font Size buttons: Click these buttons (or press Ctrl+] or Ctrl+[) to increase or decrease the point size by the next interval on the Font Size menu on the Home tab.
Click the Increase Font Size and Decrease Font Size buttons when you are dealing with fonts of different sizes and you want to change the size of all the letters. Drag over the text to select it before clicking one of the buttons.