For those who really want a PDF annotator, Sony sells a large mostly-equivalent of this, there's the Sony DPT-S1
https://pro.sony.com/bbsc/ssr/product-DPTS1/?PID=I:digitalpa...
This is a pro device, costs almost $1000. I don't own one but a friend does... it's very magical looking, and feels nice for the 2 minutes I used it.