To undo a step in Adobe Photoshop, use the following steps: 1. Open the file that you want to undo. 2. Choose the “undo” button on the bottom of the screen. 3. The “undo” button will undo the current step, and any previous steps in the file. 4. If you want to keep working on a layer, select it before pressing “undo.
There are three undo steps: one for the active layer, one for the previous layer, and one for the current layer.