I eat up mistakes without having a mouth, and get smaller each time. What am I?

I come in sheets with lots of tiny air bubbles. I am used to protect things when they are transported. It's fun to pop me! What am I? Solve the riddle → I play music and make the sound louder. I often stand on a table or a shelf. What am I? Solve the riddle → I am full of things you need for school, but I eat nothing and have no mouth. What am I? Solve the riddle → I show you the way when you don't know where to go. What am I? Solve the riddle → I have a sharp back but cannot scratch myself. I can cut almost anything, but I am always whole myself. Solve the riddle →