You can download a free non-limited edition version of the online pass from the BF3 in game store but it will not include Back to Kharkand. If you find your online passcode you can redeem it on your account at a later date (if this is a brand new sealed version of the 2011 LE copy of the game), if you purchased a used copy of the LE game you are not entitled to B2K because the entitlement has already been redeemed by the original owner of the game and you will need to purchase B2K separately.