In Windows 10 you have the possibility to scroll inactive windows (Start > Settings > Devices > Mouse > Scroll inactive windows when I hover over them).

You only have to hover over the inactive window with the mouse and you can scroll. It's the same with zooming. When you press CTRL and scroll, it zooms the window under the cursor of the mouse. It works with all other apps, i.e. MS Office, even other Adobe apps like Illustrator, InDesign, etc. but not with Adobe Acrobat. You have to actually click (activate) the window with PDF for that to work. Will it be changed?