If you've played the game by now you probably noticed that the UI is very hard to read at times due to the resolution of the screen. So after a bit of research I found a simple solution on the forums and decided to make it a bit more visible.

First of all, disclaimer, even though you do not have to change your desktop's screen resolution you will have to change some settings for the executable. The UI will be a bit more visible (and easy on the eyes) but you will not be able to change the resolution of the game entirely the way you want.

After you open Steam, search for Age of Empires II HD, right click on it then click on "Properties".

In the new window, click on the "Local Files" tab and click on "Browse" in order to open your game's install folder.

Search for the "AoK HD" file, right click on it and select "Properties". Go to the Compatibility tab, then click the "Change settings for all users" and in the new window click on the "Change high DPI settings" button and check the option: "Override high DPI scaling behavior".

Lastly, set "Scaling performed by" to "System", then click on "OK" until you exit all the "Properties" windows in order to apply all the changes.

This should be it

Please note that this this guide was created just to help some people that are struggling with the resolution. The workaround to the screen resolution issue was posted on a discussion on the Steam Community by the user: ToniSimoni, so thanks to him this small fix was found.