Can I get Minecraft Pocket Edition for free if I've already bought the game?
No you cannot. The game is only available from the Play Store, for Android, or iTunes for iOS, and you must purchase it from there.
It is a separate product, so it is exempt from the Alpha/Beta All/until release future editions free promise.
Minecraft PE is £5.00 (pounds) £7.00 (dollars)
They are separate games so you cannot get Minecraft PE for free.