[REQ] How to extract Sony Reader books (preferably into PDF)

Hello! I've got a few e-books I wanted to share here but the problem is that I don't know how to download the books I bought and turn them into PDFs without screenshooting every page. They're a few hundred pages and screenshooting means inevitably loosing quality so if there was an easier way to do so, I'd appreciate it if someone could tell me!

Have a nice day!^^