The software doesn't have a pause button or function, but that wouldn't be necessary because a typing tutor or trainer will test the way you type in an interval of time. Implementing a Pause function will decrease the stats and wouldn't be accurate at all.
However, you should forward this request to the developer through the proper channels. Ticketing system available at: https://sourceforge.net/p/ultimatebot/tickets/
The online version supports pause, but that is entirely automatic as it uses the text you added and then types it automatically on the selected websites.