As for content`s uniqueness - you can use paid or free checking software. One very well-known paid software is Copyscape. As for a free one - you can use Advego. Well, Advego`s menu language is russian, but you only need 1-2 buttons anyways, so you can use Google Translator or PM me to translate you the buttons. I am not russian myself, it's just I learned it 2 years in elementary school, and my mother language is quite similar to it, so I understand it and can help out with that.
Now about the grammar, spell checking and such - in our content company we are using Ginger. It's free and if you use it right - it's very useful. One thing you should know about Ginger however - it's not 100% right. It's good on catching grammar, spell and punctual erros, but it's not 100% accurate and it's even worse when it comes to semantic errors. Now don't get me wrong - the software is great. Using is properly can make your articles good enough for native english speakers to read and understand perfectly. But my advice is - don't trust the software for every mistake it points out - think before you edit even a single word. Ginger is way better than Microfost Word when it comes to errors edits, but it's not perfect.
Best regards,
Axeny