Allow for inverting colors of a document opened in the app. Nothing fancy like iOS smart invert needed; just invert all colors in document ignoring menu and drawing/highlighter colors. My eyes are sensitive to light, but I need to use an iPad to be able to view my textbooks in large print and take notes; I literally use sunglasses while studying, cause I require the contrast so lowering brightness doesn't help. Smart invert also doesn't work, and regular iOS invert is annoying to turn on and off as I am switching back and forth between apps during long and short study sessions.

With 8 years of undergrad study behind and 6 years of grad school ahead; I have and will continue to be a dedicated Goodnotes user; couldn't be this far without this wonderful app. I use it on both my iPad and on my mac using iCloud sync.

This is a necessary feature that will literally save tons of headaches.

Please implement this.