Epic Pen lets you write and draw over any software. It's a screen marker and digital whiteboard tool for Windows.

Epic Pen is a small toolbar that sits on top of other windows, and you can easily select cursor, pen, eraser, pen size, undo, and clear screen. A screenshot function is available. It's simple to use and learn. The third screenshot below shows us writing over Google Chrome within minutes of starting.

As a freemium product, purchasing gives you Line Tool, Text Tool, Whiteboard, and Blackboard, and Vibrant Color pack.