Is there a provisional literary work copyright?

You get copyright automatically. But if you want to win a copyright lawsuit, you file and pay the fee. That's how it is in the US. Undoubtedly it's different elsewhere.

To keep your beta readers from copying, send PDFs and not Word or MS docs.

A person who is determined to copy your book will do so. Essentially, you've made it harder. But it's never going to be impossible.

Also, no matter how much you love your work, you're not JK Rowling or Stephen King, etc. The chances of your rough stuff being pirated are vanishingly small. After publication, if your work sells is when you need to worry. In the US, the remedy is a DMCA takedown notice.

If you want, have your beta readers sign something-- and recognize that you've just told aa bunch of volunteers that you don't trust them.

Or, go on Fiverr and hire paid beta readers.

Thank you so much!! The way you explained it was really clear. And thanks for the PDF suggestion, I hadn't thought of that.