PR (besides the fact that it's useless) is totally unrelated to Adwords usage. Anyone who says otherwise is 100% misinformed.
Well since more recently sites are using peoples ads (cached) as their 'actual' content, it's hard to say. My guess is though google could somewhat easily filter that for pr purposes. However google isn't the only engine - I've been noticing it showing up a lot lately in pdf cached/mfa sites.
its celar adwords advertising wont help directly. in longterm people my come to know your site better,.. and hopefuly use it more often. That help
The natural rankings and PPC sides are totally separate. One does not help the other. What PPC can do is allow you to get exposure for keywords you cannot rank naturally for. But it won't help your natural rankings. Think about it. If that were the case, all anyone would have to do is run an Adwords campaign. Your natural rankings must stand on their own. It's called relevance which is Google's mantra. Artificially influencing relevance would essentially destroy relevance.