I want to know if writing articles and PRs with anchor links will help to optimize keywords and site?
Yes, but when your article & Pr contains unique and fresh content. Also it give results if you did submissions in to major Article & Pr sites. Dont use excessive hyper-links for your keyword anchor text because major sites hate this and consider it as spam and reject your article or pr so take care of this thing also while doing article & pr submission.
Yes these are right facts that articles and press release submissions boosts a website ranking in search results. But make sure your content which you are going to submit must be unique. Most of the websites doesn't accept duplicate content.
Yes articles and pr are help a lot to optimize a particular keyword or a website. Article boost your ranking on searching if it is unique and good content.
As long as you are submitting unique, quality and useful articles people will be entice to check your anchors. Make sure though that you are not over-stuffing keywords/anchors in your articles because most decent article directories would not accept it.