The Pathfinder SRD entry for the Disguise (http://www.d20pfsrd.com/skills/disguise) skill only mentions a +10 bonus, and the Polymorph (http://www.d20pfsrd.com/magic/all-spells/p/polymorph) spell description and polymorph subschool (http://www.d20pfsrd.com/magic#TOC-Transmutation-Polymorph) entry don't change that number.  Based on what I've found from a quick Google search, the description for the magic originally said +20, but they knocked it down in line with the skill description's +10 in errata. ^^;