Pristine Hide is the main hide introduced in Cataclysm, so it can only be obtain by skinning creatures from Cataclysm zones. Only creatures between level 78 to 86 will produce Pristine Hide. There is not an efficient way to farm Pristine Hide directly as the drop rate has been decreased dramatically. So the only and most effective method to farm Pristine Hide is to farm for 5 Savage Leather to craft a single Heavy Savage Leather as a Leatherworker. With 10 Heavy Savage Leather it can be traded with a Leatherworking Supplies that can be found in all main cities and Twilight Highlands.
So if you are a Skinner as well as a Leatherworker then you will need 50 Savage Leather to craft 10 Heavy Savage Leather to buy 1 Pristine Hide.
See below to farm Savage Leather :
Mount Hyjal (425-450)(level 80-81)
1. Fleeing Stag
2. Spinescale Basilisk
Uldum (465-525)(level 82-85)
1. Riverbed Crocolisk, Stillwater Slitherer
2. Venomblood Scorpid