Home » Tip of The Day » Get 1,000 UndosGet 1,000 Undos February 2, 2017. Posted in: Tip Of The Day. Press Ctrl K (Mac: Command K) to bring up the Preferences panel. Click on Performance, and change the number of History States (number of Undos) up to a maximum of 1,000. Note: A high Undo number may affect the performance of your computer. « Previous Photoshop Tip: | Next Photoshop Tip: » Sign-up for the PTC Newsletter so that you'll never miss a tutorial!. Your Email Address: