First, we are making a function new_window that would be the second window. The original window, root, is titled "Sound Book", says "Find how much sound your favorite book has", includes a button that states "Let's Start", and when that button is clicked, the new_window opens with the help of the command function.
While I marveled at the fact that I now knew how to make multiple windows, I also realized that it doesn't get me anywhere closer to my goal, which was to write a code in a way that would allow users to upload PDF and see how much sound it has. In fact, I didn't even need to know how to create several windows at once.
Once again, I spent a solid hour hunting for something that would show me how to do just that — upload a PDF file when using the interface. For that, importing filedialog was crucial, and GeeksforGeeks
had a great tutorial on using the askopenfile function.