I finally figured out, how to increase the extremely small font size of this game. So if you’re having similar troubles, just follow these instructions:

1. Goto data-folder, which is located in King’s Bounty’s installation folder.
2. Create Mods-folder
3. Open data.kfs (which is located in data) with 7zip (or similar program), and extract fonts.cfg to the created newly created Mods-folder.
4. Open the extracted fonts.cfg with notepad.
5. It looks like something like this:

Fonts {
...Font = clibri.ttf

......ft1_12 {
.........default=font,14,1,1,0,0,0
......}
......ft1_12b{
.........default=font,14,1,1,0,0,0
......}
[and so on]
}

6. The bolded number is the font size, so increase it to enlarge the fonts. 2 should suffice, although I raised it by 4. If you increase it too much, some clipping might occur.

There you have it! Have fun with King's Bounty! :)

This should be pinned; font size is one of the reasons why I don't play many RPGs in the full 1900x1200 resolution.

Is there a step missing because this didn't do anything for me.

Don't help me too.
Macbook Air 2011.

This Worked for me, Thanks Wartath. Just follow the instructions and make sure to to all changes until the end of the fonts.cfg

I did not get the fonts increased (I'm playing on Windowed mode)

What should be the name of the Mods folder and where should it be kept?

Ok, it did not work for me in the /data/mods/ dir, but if I moved font.cfg to /data/ it worked!

Thank you very much.
This helps a lot!

Edit:
I didn't make a new folder, just changed the ones to twos in the File.

Thank you for this thread. You've made the game far more enjoyable for me.
I do have a suggestion:
I don't think you need to extract data.kfs or make a Mod folder.
Go to the data folder. Make a copy of fonts.cfg. Rename the copy "fonts.cfg.backup". Edit fonts.cfg as outlined above.