If you have received a warning in Google Webmaster tool than it will take a lot more than just some massaging but if you have not received a warning then redo all your duplicate content by adding more paragraphs and moving existing around and removing it where it makes sense.
Then add links at high PR sites and create Web 2.0 sites and blogs to support the site.
That's big issue to have Duplicate Content over Web pages When Website Becomes Popular . One of Better option is Update Your Content "informative as well unique " And Then Again Promote Website . Be Smart and place your targeted Keywords with in Content "Looks Natural" .
Duplicate Content is not a good thing for a website ranking anytime google can punish you so it would be better if you change your website content and never use duplicate content you can check your content before you use...
According to panda and penguin, we don't have to use duplicate content if we use duplicate content then our sites would be penalized so you should delete duplicate content to get maximum benefit I would say.