So firstly, printing actual copies of your book to give to beta readers is a really bad idea. It costs loads of money when they could be reading it on the internet. When you are actually submitting to an agent or publisher, I would also highly recommend doing it electronically as that helps things go faster.
If you're absolutely sure that you need to print copies to give to beta readers, then here's some print-on-demand companies you might want to look at. A print-on-demand company is exactly what it sounds like; it prints on demand.
I'm not a salesman of any of these companies, I'm just pointing them out. However, I will forewarn you that actually printing copies of your book costs quite a lot of money if you're just going to give it to a few people. Whenever I've printed my work into a book, I've only done it for novelty purposes. Whenever I've wished to have beta readers, I've always given them the book electronically.