There are several ways to annotate PDF documents on an iPad with newer versions of iPadOS and iPad apps. This page highlights two ways to annotate PDFs on an iPad using Google Classroom.

Annotate a PDF with Google Classroom iPad App

(5 Steps)

Annotate a PDF with Google Classroom in iPadOS Safari

(11 Steps)

A longer (4 minute) video version of these steps is also available, specific to 6th Graders in Mrs. Rumbaugh's Math Classroom. This version shows the STUDENT VIEW in the Google Classroom app, including taking a SCREENSHOT of a completed assignment before making corrections in class and turning both files in for a grade.