When Artisans were first announced for Diablo III, they came in three forms—the Blacksmith, the Jeweler, and the Mystic.
The Mystic was originally intended to create scrolls, brew potions, and produce magical weapons, spell runes, and charms. Furthermore like the Enchanter in Torchlight II, she could also imbue your items with additional enchantments.
Due to the changes to the skill system and balance-related issues, the Mystic was removed and some of her skills (namely the production of magical weapons) were handed over to the Blacksmith. Likewise, the ability to socket items was given to the Jeweler.
However, despite the fact that socketing is listed as one of the Jeweler's abilities, the ability seems to be missing from the game. The only way you'll get a socketed item is through sheer luck. You won't be able to add new sockets to a preexisting item.
Like the Mystic artisan, such features are likely to return in an expansion pack or future update for the game.