Hello ZephPettitt
Welcome to the Microsoft community.
Based on your current description, it seems that OneNote 365 is blurry when paired with a 4k monitor, as the screen output is usually related to the software and hardware:
Could you please share information about the current hardware information of your computer's graphics card? For example, Nvidia/Intel/AMD?
If it is convenient, could you please test the issue, and is the current blurred display only occurs in OneNote 365? Does other applications behave normally?
There are a few things you could try to fix the blurriness in OneNote:
Make sure you are using the latest version of OneNote. To check for updates, open OneNote and go to File > Account > Update .
If you are using a high-resolution display, try changing the scaling settings for OneNote. To do this, Press Windows+E > then go to the following path "C:\Program Files\Microsoft Office\root\Office16" to find ONENOTE.EXE
right-click on the OneNote icon and select "Properties". In the "Compatibility" tab, under "Settings", check the box next to "Override high DPI scaling behavior" and select "System (Enhanced)" from the dropdown menu. As shown below:
I hope these suggestions help! Let me know if you have any other questions or if there is anything else I can assist with.
Chandy |Microsoft Community Support Specialist