Unfortunately 3DXchange 7 doesn't fully support 4K or other Ultra HD monitors but the workaround below may help.
Please try the following with 3DXchange 7 closed down.
1. Right-click the 3DXchange 7 desktop icon and select Properties.
2. Select the Compatibility tab.
3. Once there, click "Change high DPI settings".
4. On the second dialog box that opens, go to High DPI scaling override.
5. Check the "Override high DPI scaling behavior" box, and from the drop-down select System (Enhanced).
6. Click OK, and then OK again.
7. Now try opening 3DXchange 7 again to see if scaling is better.