In my own experiences, there might be no keyword tool would help your sites in increasing PR. You need to use them and target the right keyword for your sites niche-accordingly. As for PR purpose, keeping your sites with niche relative fresh contents plus enough quality back links using your targeted keywords as anchor text would be top issues. :)
Personally, I use keyword elite for keyword research purpose.
I use http://www.keywordsnooper.com/ to find hundreds of long-tail keywords, and use it together with Google Keyword planner to manage as many keyword research projects as I need. This is by far the easiest to use KW tool and the most affordbale one.
Thare is no any tool for increasing your page rank. It depends upon the internal links and do follow external links. after calculating all this links Google raise the page rank of the webpage in the website.