If you do not want to write fresh content yourself or you do not have time, I suggest you outsource the job. Make sure whom ever you outsource to is writing them from scratch and not usinga spinner themselves. My favourite are seoarticlewritingpros.com but you can also outsorce companies like www.contentproz.net or www.articlewritingservices.org plus loads of others too.
Seriously noone has mentioned Unique Article Wizard? Check it out it blows the other 30 or so article writers I've tried out of the water. It contains a synonym database updated by users so the synonyms actually make sense and are available for entire phrases as well. There is no magic pill that lets you click a button and bam you have a new unique article. That doesn't and will never exist so stop lookin if you are(or squander your hard earned $ on failware)!
To rank your website in search engines you have to post content at your website on daily basis. If you have more than 2 websites then it is almost impossible to write unique content on all those websites. To do this task webmasters use article spinning tools so that they can post articles to their domains daily. Paraphrasing Tool is also used by students when they have less time to submit their assignment; they just copy content from the internet, rewrite it, remove grammar mistakes and submit it.