The folks of Sammobile.com scored an Android 4.3 test firmware for the Samsung Galaxy Note II and below you can find both the download link for the preliminary release and some instructions on how to get it to work.
The test firmware is version N7100XXUEMJ5 and it’s available for the Note II version GT-N7100. Samsung is expected to start rolling out the official update to Android 4.3 for the Galaxy S III and Note 2 in November, so we have to wait a bit. If you don’t like waiting, you can go with the pre-release firmware, that you can download from here.
This is a test firmware that will not void your warranty and it’s all pre release, so not official from Samsung. You need to unzip the firmware file, download Odin3 v3.09 (from here), extract the Odin .zip file and open Odin3 v3.09. Then you restart the handset in download mode (hold Home + Power + Volume down buttons) and then connect the phone and wait till you get a blue sign in Odin.
The rest of the instructions can be found in the source link below, but overall it’s a pretty foolproof process.