The option to print a bill that has been marked as paid isn't available in QuickBooks Online, liz.
There are possible ways on how you can do it. I'm here to help you.
Firstly, you can utilize the print screen ability of your computer. Use the Windows logo key + Shift + S to make a quick screenshot or use the snipping tool by searching it on your Windows search bar. Once done, paste it into any word-processing platform, and then from there on, you can print it.
Another way to print it is to use the keyboard shortcut Ctrl + P. This will open the print window and show you a print preview of the current page or document on your screen.