Hi
I am new to SEO field so could any one suggest for my question

No. Page Rank (Which is usless by the way) is determined by the number and quality of inbound links pointing to your site.

Jamie

Jamie is correct. Having a forum does not increase your Page Rank.

Jamie is correct, but a large enough forum which is well known and has plenty of links to, would help the forum pagerank and possibly the site as a whole if there were links etc. to it. It's probably not worth the bother though and as Jamie said, pagerank isn't very important - quality traffic is what counts

if you have a forum on your site it does help page rank a bit as you're adding a lot of content to the site regularly.

posting links in forums doesn't up your PR but it does get your site crawled quicker!