If you're cheap like me, just paste them on blogger and check with Copyscape. Create a new blog everytime you reach Copyscape's limit.
Here's exactly what I do. If you're using Firefox, you can right click the search box of Copyscape then click 'Add a keyword for this search'. In my case, I set the keyword to 'c'.
Now, I'll paste my article to my dummy blog. Let's say my blog's address is: hxxp://dummyblog.blogspot.com. I will then open a new tab and enter this in my Firefox address box:
Code:
c hxxp://dummyblog.blogspot.com
Notice the 'c' before the blog url. It will now return copyscape results for my article. After that, I'll go back to my blog and edit my first post with another article. Back to my copyscape tab, then hit 'F5' for refresh. Just click 'Resend' if a notification pops out.
If you're used to it, you can check 5 articles in less than a minute.
Otherwise, just pay $5 for 100 searches.