This question gets asked by readers a lot here at Indies Unlimited: How can I protect my manuscript from being taken by someone I let read it? And as common as the question is, it’s an easy answer: you can’t.
That’s not the answer most people want to hear, but Indies Unlimited is an “Alternative Facts Free Zone,” so only the truth appears here. And the truth is, you really can’t stop someone from doing unauthorized things with a document you give them.
The good news is that most people don’t do untoward things with your document. Most people do what was asked: read your manuscript and then either provide you feedback or write a review. However, occasionally, an unscrupulous person may share your book. Like I said, there’s really no way to stop someone who wants to do wrong with your file, if they have it.
While you can’t guarantee anything, there are some things that people do to try to prevent readers from sharing their work, taking credit for their work, or uploading it to pirated book sites.