Pro Tools does apply dither automatically in some very specific situations that you don't need to worry about, such as after processing through upsampling plugins but before sending the audio to the Master Fader at the Session bit-depth.

Does Pro Tools dither on export?

And you can't stop it. If you are exporting a 24 bit file as a 16 bit file, Pro Tools automatically applies dither and noise shaping to your export.

When should dither be applied in Pro Tools?

The simplest way to look at it is that you should always dither when going down in bit-depth. So, if you're going from 24-bit to 16-bit, you should dither. If you're going from 32-bit fixed point (not floating point) to 24- or 16-bit, you should dither.