Reader will not install

Are you talking about adobe acrobat reader? If you are it could be an update because i had the same problem with another app also check your storage because it can cause problems if it's nearly full or if your having problems installing an app probably contact apple support they would give you a few ways to fix the installing problem. But there could be another problem as well if its not installing it could be if your using a school wifi the school would probably block you from installing some apps wich means you need to install it at home. If this helped reply to what helped if its the school wifi stop trying installing this stop it and install it at home so it will work.