This article explains how to scan documents using the Notes app on an iPad running iOS 11 or later. It also explains what to do after you scan the documents.
Scanning Documents with an iPad
Starting with iOS 11, Apple added a scanning feature to the Notes app. This allows you to capture a document and save it to your iPad in PDF format. Here’s how:
Place the document on a flat surface with sufficient light and preferably against a contrasting background.
Tap the pen and paper icon to create a new note (or select an existing note).