I read this Google AdSense program policies allow you to place up to three ad units and three link units on any page. so can I put total six adsense for content on one page?
According to the guidelines yes. But, it's been noticed that if you have a lot of adsense on one page the CPC goes down.
You can put 6 ad units with out any doubt. Google allows 3 units per page of one category that is ad units is one category and link units is another category. So no problem to use 3 ad units and 3 link units per page.