You may notice that in iOS 11, if you take a screenshot, a small thumbnail will appear in the bottom left corner of your screen. This new feature makes it easy to quickly draw onto a screenshot before saving or sharing it.
Simply take a screenshot, tap the thumbnail, and then use the pen tools to draw on the screenshot. At the bottom, you can choose between a pen, highlighter, and pencil, or change the color of your annotations.
Tap the Share icon in the bottom left to save or share the screenshot.
If you don’t tap the thumbnail, it will disappear after a few seconds. Alternatively, you can swipe it off screen if you want rid of it quickly.