Is there any way to increase the font size?

You can edit winpref.js in your K-Meleon/defaults/pref folder. Mind that those are the default preferences but this is actually the easiest way to universally increase font size.

If you feel at home with macros, you can also take a look at
<a href>http://kmeleonbrowser.org/forum/read.php?f=1&i=1933&t=1933</a>;
The text of the config files contains a 5-size font macro with a separate menu.