High quality inbound links will drive traffic to your website and improve PageRank. Inbound links are like getting "the vote".
Consider inbound links as the "currency" in use to rank websites. A website with a greater number of high quality inbound links will achieve a better search ranking than a website with a higher count of links that are of lower quality or Page Rank.
That being said, not all inbound links are created equal. Your focus should be on acquiring high quality inbound links from an authoritative website. An authoritative website will have a high (6 or higher) Page Rank.
What is Google Page Rank?
Content and PageRank
While adding daily content for your website is recommended to satisfy your visitors, it does not improve PageRank. PageRank is directly related to the value of inbound links to that page. However, adding daily content to your website will attract links while keeping your text links natural which is what you want for your website.
Low Value PageRank Link Exchanges
When exchanging links with other webpages, you should never focus on PageRank as the primary reason for the link exchange. Your focus should be on your visitors. Keeping your visitors your first priority, ask yourself would this link be of value to your reader in discovering new and interesting information relevant to your niche.
There's nothing to say that exchanging links with a PR2 site is a bad thing. That PR2 site could become a PR7 site and your link is already established and as a result you improve PageRank.
Count of Inbound Links
Will having more inbound links improve PageRank? How many inbound links are too many?
If a page has over 100 outgoing links, they are considered to be link farms in the eyes of Google. If a web page has linked to you multiple times from one page, you may want to use Google's link disavow tool to ensure your site is not penalized for another webmaster practicing black hat SEO.
Keep in mind that your PageRank can take a hit if you lose inbound links coming from high PR sites. Your PageRank can also decrease if a site linking to you experiences a decrease in their PageRank. It's a domino effect, if one web page experiences a decrease, that same decrease is filtered down to all the linking partners of that page.
Like I've said before, inbound links serve as referrals or votes for web page. This is why attracting an inbound link from a webpage with a high Page Rank is considered of greater value than 2 inbound links from a webpage with a lower PageRank. The greater the PageRank, the bigger the vote.
In summary, your link building strategy should include attracting high quality inbound links. This in itself will improve PageRank. Adding daily content to your website will keep it fresh for both the search engines and your visitors. If your website content is unique and of high quality, others will link to you without you having to make the request.
Watch and Learn: How To Build A Quality Links Program