You can scan documents/textbooks and turn them into a PDF by using either the Adobe Scan app or the Office app. Adobe Scan offers easy PDF scanning that also automatically recognizes the text (therefore increasing accessibility). Remember to sign in with your campus account.
The Office app also allows for scanning documents into PDFs but also allows for scanning a table and turning it automatically into an Excel spreadsheet, scanning a document into a Word document, and even creating a PowerPoint presentation straight from your phone. The app also lets you see all your OneDrive documents in one place. Remember to sign in with your campus account.
Google Drive Android
The Google Drive app on your Android phone can scan documents and upload them to your Google Drive. This app does not work on Apple phones.