I'm rendering on screen the game fps using bitmap font but there are no methods for the size. This is a problem for me because my camera viewport size is very small so the text when rendered is huge and pixelated.
font.draw(batch, Float.toString(Gdx.graphics.getFramesPerSecond), x, y);
Did you try setScale() method that what i use to resize my font
myFont.getRegion().getTexture().setFilter(TextureFilter.Linear, TextureFilter.Linear);
myFont.setScale(scale);
if you have trouble, leave a comment
Good Luck !!
Edit :
With the latest libgdx version, try to scale font like this :
myFont.getData().setScale();