How to know whether a potentiometer is a linear potentiometer or audio potentiometer?
The relationship between the angle of the knob and the resistance is the "taper". That datasheet says this pot's taper is "1B".

Finding information on what 1B means is a bit tricky. It's at the related information link at the top. The tapers are described at the very bottom. Here's the relevant image:



It's hard to read, but 1B is the straight line in the upper-left. This is an ordinary linear pot.

This is something of an industry convention. See for example Alpha's pot tapers. By convention, anything with a "B" in it is a linear taper. Anything with "A" in it is "audio" or "logarithmic".