It takes one click to add a watermark to all the slides. Using a Watermark in PowerPoint Dec 21, 2024 — To use a watermark in PowerPoint, you first need to define its size, then, with the slide master as the active item, you'll be able to move its shape and the color it appears in. There's another way to assign a color to the watermark, as I do here. If you have trouble choosing color from a set of colors in PowerPoint, click here.