Could you be a bit more descriptive? Are you talking about dragon hide used to make armor, a class or racial feature, or a spell?
Edit: Nevermind, I see it now.
Dragonskin grants a + 3enhancement bonus to natural armor +1 per two levels above 5th level (to a maximum of +5 at 9th level). (Source: Spell Description, Daconomicon page 112)
or
Dragonskin grants a +4 enhancement bonus to natural armor. (Source: Sorcerer/Wizard spell list, Draconomicon page 108)
I assume there's some sort of errata, though I'd go with the spell description.