Examine the free plagiarism checker at http://searchenginereports.net/articlecheck.aspx
This website allows you to enter text by cutting and pasting, uploading a file or entering a URL. You also can adjust the sensitivity of the program. It will generate a free plagiarism report so you can see exactly which areas may have problems.
Consider http://www.grammarly.com
Grammarly calls itself the "World's Most Accurate Grammar Checker," and it also offers a Plagiarism Checker tool. The plagiarism tool pairs with grammar scanners and spell check and is part of a larger report generated when you submit your paper with Automated Reference Creator. The website will detect plagiarism and note it in the report, and the Automated Reference Creator will try to create corresponding references for your work. The free service offers other tools, including a Vocabulary Enhancer.
Another option offers you service at http://www.dustball.com/cs/plagiarism.checker/
This website, sponsored by the University of Maryland, allows the writer or reader to copy and paste text into a plagiarism checker. The result indicates how much and what exactly has been plagiarized in the paper.
Investigate another free tool at http://plagiarisma.net/
Plagiarisma.net offers itself as a "free on-line plagiarism checker and duplicate content checker." The site supports over 190 languages and allows you to check text by uploading a file, coping and pasting or entering a URL. This site reads TXT, HTML, RTF, DOC, DOCX, ODT and PDF files.