I have this wonderful little clip-on tuner called the PolyTune Clip Black from the same manufacturer, which works so well and is packed with a lot of features (alternate tuning, strobe, set reference...) and needed the same in a compact pedal format. Unfortunately, this pedal does not meet the expectation: into this pedal, there is not half the feature of the clip-on tuner, and especially there is no way to set the reference so you are stuck with a 440Hz tuning.
Also, that little sheet of paper thrown into the box cannot be called a user's manual.