I was told that there is a rule (which i can't find) that says that you can stand up from prone using a full round action without provoking AoO, does such a ruling exists?
Short answer: No.
Long answer: Nooooooooooooooooooooooooooo.
Seems like a reasonable house rule, but standing up is a move action that provokes. There are some abilities (typically feats for monks, but there's a Rogue talent, too) that allow the character to stand up as some other kind of action (usually swift). They might still provoke, though.
Monkey Style (Combat, Style)
Your unarmed fighting style is nimble and unpredictable, full of ground rolls and short leaps.
Prerequisites: Wis 13, Improved Unarmed Strike, Acrobatics 5 ranks, Climb 5 ranks.
Benefit: You add your Wisdom bonus on Acrobatics checks. While using this style, you take no penalty on melee attack rolls or to AC while prone. Further, you can crawl and stand up from lying prone without provoking attacks of opportunity, and you can stand up as a swift action if you succeed at a DC 20 Acrobatics check.
Normal: You take a –4 penalty on attack rolls and AC against melee attacks while prone. Standing up is a standard action that provokes attacks of opportunity.
Thank you for the clarification.