How to adjust size of icons in Creo 4.0 ribbon?

I'm don't think you can change the actual icon sizes but you can hide the command labels.

Before:

After:

How to hide them:

This might be worth reading as well:

http://support.ptc.com/help/creo/creo_pma/usascii/index.html#page/fundamentals%2Ffundamentals%2Ffund_three_sub%2Fabout_ribbon_resizing.html%23

@ptc-6749480 

Icon in Creo cannot resize. When resizing the Creo Window group/icon can collapse as  it works on group policy to decide which group needs to collapse first. 

Contrary to what @TomU and @Mahesh_Sharma said, you can resize icons (you can switch between large and small version of the icon). To change the size of the icon, first right-click the ribbon and select Customize the Ribbon to display Creo Parametric Options dialog box. Then you can simply right-click desired icon and select Small Button or Large Button to set the icon size.

For example, all icons set to Small Button:

And all icons set to Large Button: