This trailer has got four main features:
1. automatic steering axle - This is one of the best feature in this trailer. It works fully mechanically and thanks to that the turning radius is quite small.
2. adjustable collector (PF M motor)
3. extendable slide (PF M motor)
4. tracks propulsion (PF L motor located in the tractor)
The collectors reliability isn't 100% but I think it can collect paper pieces well.
If you are interested to know more about the tractor, check this video.