If you purchased Assassin's Creed III Season Pass you can access all DLC with the following links:
DLC1: http://goo.gl/ah2m5
DLC3: http://www.mediafire.com/?cjkpbdmk19lr96g (Torrent)
DLC4: http://www.mediafire.com/download.php?a8ebzva1tcyer6k (Torrent)