Actually, in several interviews with Google officials, they have made a point to specify the duplicate content is based on two precise criteria: the intent to manipulate and to be malicious. They have also said that they understand that not all duplicate content (including article marketing) has the intent to manipulate or be malicious.
You do not have to and you have never had to change anything about your articles before you submit them. This is another giant Internet myth that has run rampant due to lack of education.
Google understands that articles are a savvy marketing strategy and they have been long before link popularity and search engines took over. Write good quality articles and add them to your site. Then submit them to places that it makes sense to submit to. Google won't "penalize" you for it.
It would be helpful if people would spread the word about this just as they have helped to perpetuate the article myth. Let's correct this assumption and save ourselves a lot of extra and unnecessary effort.