the best PDF editor i've used in Windows is Drawboard.
https://forums.windowscentral.com/e...d-pdf%2F9wzdncrfhwqt%3Frtc%3D1&token=1VhQwvAo
It feels designed mainly for architecture or engineering, however I use it for my PDF textbooks and the activity book I have in my French class.... I write on it by hand, and it has A LOT of features, just be sure to learn a little how to use it because there will be things you wont find, but chances are that the app has it buried somewhere...
The paid version allows you to create new PDF documents, merge, rearrange, etc and the new pages can have plenty of paper backgrounds, it has a protractor ruler and many other annotation tools...
It is definitely one of my favorite apps on Windows. However I use another PDF reader by default because it is faster to open and just read the document, though it has no additional tools..... but I use Drawboard a lot more.
Other nice apps to have in my Surface Book and your Pro 4 would be Enpass (a password manager compatible with Windows Hello), Todoist (a To Do organizer app available for all platforms)...
My Study Life has great ratings (I haven't tried it yet).
Office Lens is a great Photo-to-PDF app (like CamScanner)
There are many others, take a look at the Windows Store and filter results by "Best Rating" and the category of your choosing...
It is obviously not the App Store or the Play Store, but it does have plenty of must-have apps...
Diego.