I'm on Kubuntu, and I want to use MINT.
Can I switch distributions without losing any file?
You actually can. When you boot up the Mint .iso, you can select "Install Linux Mint" icon. It will prompt you with two choices of how you want to install it: "Install Linux Mint alongside (The currently installed OS)", and "Erase disk and install Linux Mint". You want to select the first option. So when you do that, and get everything set up, you will be dual-booting Kubuntu and Mint. Hope this helps.