A Global Change is a pre-defined task or sequence of tasks provided to you by PitStop Pro, allowing you to change a specific aspect of your PDF document, such as a color, a font, an image ... You can apply the Global Change to the whole document, to specific pages or to the selection of your choice.
Global Changes are very easy to use. You don't need any programming skills; just select the Global Change you need, set your preferences and run it.
However, they are less powerful than Action Lists; if you need to perform complicated tasks, you may be better off with Action Lists.