do global object instance and call it as "Pause Button". Make a specific event sheet for the pause function, place the button on a layout (you don't need to care about this layout, it's only to create the instance on the runtime).
On the event sheet, make it create the button where you want, then, make it become invisible with events and make some event keys to activate the visibility.
Call the event sheet on your stage event sheets.
Well, that's it, if you need more specific description, you should share your CAPX, so, We can make it for you.