What I do is create boards that very closely mirror the themes of the posts on my site and use keywords that very closely relate to the posts on my site to pin to each board.
Let's say I have a "fashion" site with 10 posts: 3 posts about women's fashion, 2 posts about men's fashion, 3 posts about fashion trends and 2 posts about fashion on a budget.
I would create 4 boards in the Pinterest account:
Fashion on a Budget
In SM2 I would create 4 pin jobs -- one for each board.
For example, for the Women's Fashion board I might use keywords like "women's fashion", "fashion for women", "top women's fashion", etc. I would have the job pin only to the 3 pages of the site that match the topic "women's fashion".
I would repeat the process for the other 3 boards: using keywords closely related to my site pages on the topic and only pinning to the pages dedicated to that topic.
What that will do is ensure the closest match of visitor intent with page content. This helps you in 3 ways:
1. If you use AdSense, it increases the AdWords advertiser conversion rates, which increases your RPM (earnings per 1,000 visitors).
2. If you're promoting affiliate products, it increases the conversion rate.
3. It lowers the bounce rate and increases visitor returns because more people are happy with what they see on your site even if the exact image on the pin wasn't there.
I also strongly recommend you have a pop-up opt-in box that gives people a very, very good reason to opt-in. That puts them on your email list and gives you the opportunity to return them to your site by emailing them about the other site pages / topics and/or sending them promotions (within reason).