Depends on which one, since there are plenty of free plagiarism checkers available now. I'd personally recommend you using http://www.plagtracker.com/, it requires the less efforts to run the checking process.
2 Answers · Education & Reference · 24/09/2012
Sure, there are some Plagiarism checkers online that can check two papers one person wrote with other person'...
2 Answers · Education & Reference · 23/09/2011
This should do the trick: http://www.smallseotools.com/ plagiarism - checker /. It's been around for several years now and keeps on improving.
5 Answers · Business & Finance · 21/08/2013