Traktor LE can be downloaded from the Native Instruments website. There is no "Traktor LE" specific download, instead you must download the demo version of Traktor and activate it to run Traktor LE
Downloading Traktor LE
1) Visit http://co.native-instruments.com/index.php?id=tprodemoversion to recieve a download link for the Traktor demo.
2) Install the demo by following the onscreen instructions
3) When running the demo you will be prompted at start up to either run Traktor as a demo or to activate.
4) Press activate and follow the onscreen instructions in Service Center. After creating an account with Native Instruments you can enter your Traktor LE serial number to activate your version of Traktor.