Credits to Kaiell from the Official RO2 Forum for the idea.
If you are not happy with the official game font which might be because it is hard to read especially on the chat box then you can change it to any font that you like by following the instructions below:
NOTE: Can't post links yet, bear with me.
1. Navigate to ..\RO2\UI\FONT folder. It is usually C:\PlayPark\RO2\UI\FONT.
2. Find Philosopher-Bold.ttf and make a backup of this font by renaming it to something like Philosopher-Bold.ttf.bak
3. It is recommended to use Arial Bold because it looks good on both the chat and system windows.
4. Once you inputted the captcha on the site, you will need to save it as Philosopher-Bold.ttf. Yes, don't use Arial.ttf or ArialBold.ttf or ArialB.ttf. Only use Philosopher-Bold.ttf.Code:fontyukle.net/en/Arial+Bold.ttf
5. Place that font to the ..\RO2\UI\FONT folder.
NOTE: Basically, you are replacing the original Philosopher-Bold.ttf with another font using the same filename.
6. Start the Game. If done correctly, the game will now use Arial Bold as its font. If you are not happy with it, you can use any other font that you like by simply following the instructions above.