As the title. The pfsrd has only four tattoo, and I understood there are more. I'd also like to know what books they are from.
Inner Sea World Guide has the feat Varisian Tattoo that lists 7 tattoos, each giving a +1 caster level to a particular school of magic. They require the Spell Focus feat for that same school.
Inner Sea Magic has the feat Inscribe Magical Tattoo along with three different tattoos. It also has the Tattooed Sorcerer archetype.
There's the Varisian Tattoo feat that has seven different variants, one for each school of magic.
As for magical item tattoos:
There are three tattoos from Inner Sea Magic: Spell Tattoos, Reservoir Tattoos and Caster's Tattoos with lesser and greater variants of the Caster's Tattoos. These are the few on d20pfsrd.
There are four tattoos from Magical Market Place: Hypnotic Tattoos, Runeward Tattoos, Serpentine Tattoos, and Animal Totem Tattoos. Runeward Tattoos have seven variants, one for each school of magic. Animal Totem Tattoos have 11 variants, one for each Animal Shaman archetype of Druid.
And lastly, there is one tattoo from Bastards of Golarion. The Kin's Face Tattoo.
Archives of Nethys has all of these on their site, if you're looking for an online source.
And of course, as was mentioned above, there's the Tattooed Sorcerer archetype which gets more tattoos as they level, though said tattoos are merely aesthetic.
Ok, thanks. Still seems quite a small number considering the fact that you need a feat to make them, but at least it's a logical number now.