Here are 2 resources for you. If you want to check any doc, docx or pdf against another document checker than Turnitin.com try DOC Cop. It performs a similar type of search. It is free and easy to use. Simply create an account using an email address.
The second resource is plagiarism.org. This is an amazing site full of resources. It has how to’s, ask the experts and explanations of information that will help you avoid plagiarism. The bottom line is if you are worried or concerned about plagiarizing check your sources, check your information and be confident that you are creating original works. Good luck.