Hi Sendhil, there are definitely free plagiarism checkers you can use. However you should be careful with which one you choose. Some plagiarism checkers (e.g. edubirdie) aren't very trustworthy and might store or sell your document.
I'm sure you'll find my research on free plagiarism checkers interesting. You can check out the article here: https://www.scribbr.com/plagiarism/free-plagiarism-checker-comparison/