Unless the book was never originally bought on Amazon, or is not available. I have hundreds of pdfs and epubs that I will read on my Kindle, such as Homer's Odd

Unless the book was never originally bought on Amazon, or is not available. I have hundreds of pdfs and epubs that I will read on my Kindle, such as Homer's Oddesy. How do I share this? After no research done at all, I don't know how to lend/share free content.