I am trying to open a text book from an online class on my ipad so I can read it. It is password protected. How do I put in my username and password? It won't let me click on the spaces for it.
If a PDF document asks you to enter both username and password, it is likely a DRM (Digital Rights Management) protected PDF document.
Currently, Acrobat Reader mobile apps (for iOS, Android, Windows Phone) do not support "ProtectedPDF"s or DRM-protected PDFs (including text books like yours).
Would you contact the publisher of the PDF document to see if they have a solution for mobile devices?
Sorry for the inconvenience.