Currently on version 0.4.6 the right way to set font is by

:set font "foo"

The syntax is flexible. For example, setting foo to either "Inconsolata regular 12" or "Inconsolata 12" or just "12" work. However, for new users it's tempting to change font by trying

:set font "Inconsolata"

Then by default zathura set font size to extremely small. So small for the users to misunderstand. I first thought that the status bar disappears. Then after a few fiddling I figured out that it just "sank". And then I realize that it actually set the font size to a micro level.

EDIT Setting :set font "12" is actually not OK as it disables showing the box why selecting words.

What can be changed

1. A better doc for setting fonts
2. Set font to size 14 if user did not specify. Give a hint message.
3. Fix the bug after :set font 12