I have this too with acrobat dc pro, whenever I press comment, shadows under windows disappear. So once we don't have any update by adobe, I made a workaround so I don't need to turn on shadows every single time I open pdf's. I turn on the little border in windows (this is turned off, but to turn it on is very easy), i don't have the shadows but with this 1px border i always see where my windows are and it's easy to resize for example.
I have this too with acrobat dc pro, whenever I press comment, shadows under windows disappear. So once we don't have any update by adobe, I made a workaround so I don't need to turn on shadows every single time I open pdf's. I turn on the little border in windows (this is turned off, but to turn it on is very easy), i don't have the shadows but with this 1px border i always see where my windows are and it's easy to resize for example.