Will PR go down if link to a lower PR site

SHort answer?

No.

I think the only thing that matters here is the # of outgoing links you have and not the PR of the sites you're linking to.

No. Which is why you should list my PR 4 and 5 sites on your PR 9 sites.

and another answer no

If that was the case all link sites would have a very low PR

Yes and no. The PR of the page will not go down, but you can hurt your internal linking structure. Say your domain is PR5 and you've got 5 sub pages. Say all the sites you link to link back to you as well, so it's kind of an even trade. Your main page links to your teen page, and your teen page links back to your main page. See how it's a circle? You want to pass the PR along to your teen page then the teen page feeds some of it's PR back to you. The problem arises when your teen page also sends PR to alot of other sites who aren't sending nearly as much back. Therefore your teen page has less PR to send to your main page, and the cycle continues.

It's really trivial as far as your serps are concerned though. Your main page isn't losing any of it's "initial PR" and you're better off with alot of lower PR pages linking back to your site with good anchor text anyway. PR isn't the end all be all of search engine ranking and some people throw away good opportunities focusing on nothing but their internal linking structure and whatnot.