According to this site, the Jeweler can, besides removing and combining gems, also add new sockets to existing items.
I just acquired the Jeweler, but I can see no such option in his menus.
Do I have to upgrade him to a certain level to unlock the skill?
Best Answer
Diablo III Base Game
According to Blizzard, the Artisan cannot add sockets, and the game guide is erroneous (to be updated in the future):