PDF markup app for Windows. Used to be $17 I think. The price varies all the time.
From the store description-
Drawboard PDF is renowned for smooth and natural pen inking, uniquely intuitive and easy user interface, pen and touch compatibility and an impressive array of markup and text review tools. And of course, all our annotations comply with global PDF specification standards.
They also have some sort of pro subscription which is paid but optional. The base app has all the features most people need.
I bought it a while ago - it was the first app of many I tried that worked with the pen on my 2-in-1 Windows laptop for marking up PDFs. The user interface has its quirks but I'd recommend it for marking up, especially if it's free. It isn't a (good) PDF reader for general documents - Foxit Reader is much better for general reading.