While rewriting...
Make sure you alter the content structure, it is the most basic thing to do.
Apart from this, another tip to follow while rewriting is to keep a broad spectrum. Read a paragraph and then try to write it down in your own words. (Avoid rewriting sentence by sentence, instead focus on writing paragraphs at once).
Of course you can look to add something new and unique to your article, to make it different from the previous ones. There is plenty to add to every content, irrespective of how well-researched it is. Find out what you can ADD TO IT TO MAKE IT your own...