PowerPoint doesn’t allow you to perform operations on all the slides in a presentation, like scaling down the font size of every text box. (As far as I can tell, it only allows you to select multiple text boxes and set them all to the same font size, one slide at a time.) However, it does support AppleScript, which can do the job for you.
The following script will adjust every text box in the entire presentation. It won’t do a perfect job because text boxes that contain text of different sizes will be resized to a single font size. However, it can save a lot of time when you have a large translated file with broken formatting.
You can run this script direct from the AppleScript Editor application, but if you think you’re going to use it a lot then you would be better off saving it in the PowerPoint scripts folder (~/Library/Application Support/Microsoft/Office/PowerPoint Script Menu Items/), from where it can be directly accessed via PowerPoint’s scripting menu.
The script below contains two variables that you can adjust to suit your needs:
minFontSize (the font size below which no scaling takes place) and
fontScaleFactor (the factor by which font sizes greater than
minFontSize are scaled). Don’t forget to save a backup before running this script.
set fontScaleFactor to 0.65
tell application "Microsoft PowerPoint"
tell active presentation
set theSlideCount to count slides
repeat with a from 1 to theSlideCount
set numShapes to count shapes in slide a
repeat with b from 1 to numShapes
set sz to (font size of font of text range of text frame of shape b of slide a)
if sz is greater than minFontSize then
set sz to minFontSize + (sz – minFontSize) * fontScaleFactor as integer
tell font of text range of text frame of shape b of slide a
set font size to sz