So Freedom Fighters is one of the many old games that face this issue. This article is towards fixing that problem.

Instructions:
1. Download dgVoodoo2.

2. Grab the D3D8.dll, D3DImm.dll, DDraw.dll (all 3 inside the MS/x86 folder), dgvoodoo.conf and dgVoodooCpl.exe.

3. Copy all files into your main game folder (Don't copy the "MS/x86" folder, only the files inside it)

4. Configure dgVoodoo2 using the dgVoodooCpl.exe.

5. Go to the "DirectX" tab and force your desired resolution (you can also force other things like AA and AF)

6. Make sure you have "dgVoodoo Watermark" off.

7. Click Apply and close dgVoodoo.

8. Now go to freedom.ini (Location is: C:\Users\USERNAME\AppData\Roaming\IO Interactive\Freedom Fighters) and set the lowest possible resolution that has the same aspect ratio of your chosen res inside dgVoodoo. You might have to add a custom resolution in the Nvidia or AMD Control Panel.

9. Enjoy your scaled UI.

PS: This also fixes the framerate drops in Windows 8/8.1/10.

Amazing, finally some solution when the devs can't fix it themselves.

Big thanks

Wow, such detailed instruction! :) Thank you for your endeavor, now I can customize UI size with your explanation.

First off, thank you for this awesome guide, it worked!

Second off, I just want to point out that you don't need to edit the .ini file, you just need to start the game's launcher and select the lowest possible resolution (for the UI and text to be the biggest, in my case it was 1280x720), and in dgVoodoo 2 just select Max in the resolution selection and voila! 4K rendering with properly-scaled UI and text.

No problem dude. For changing the resolution manually, it's possible to go even lower and get bigger HUD, for people interested in it, it's cool to have it in mind.