Quite a while ago I promised to post and publish my Edirol PCR300 Midi Mapping for Native Instrument´s Traktor Pro 2. Here we go:
Settings to be made on the PCR300: nothing, you just use factory preset no#1 and press the dynamic link button on the left to enable the v buttons to send midi commands.
Settings to be made withing Traktor: Load the PCR300 mapping file.
Following picture gives an overview what´s going on: