DocHub

If you share a PDF with students through either Google Drive or Google Classroom, DocHub can help your students do more than just read it. DocHub with allow students to view, edit, and sign it.

If the students click on the PDF file that you have shared with them either from Google Drive or from your Google Classroom, they should have an option to "open" it with another app when they view the document. It would be in the top center of the PDF screen. If they do, have them choose DocHub. If not, they may have to click on the 3 dots in the upper right, and choose to "Open in new window" to see it (or Connect new apps to add it).

Now, they can add text, highlight, erase, etc. Then they can share it back to you in Google Drive, or attach it back to you in Google Classroom. Either way, they have to go to file (3 bars in the upper right on DocHub) and choose to Export it. Then, they can share or attach their newly changed PDF.

Here is a tutorial on using DocHub, and how to make a paper assignment a PDF to use with DocHub.

Since DocHub only works with PDF, find out here how to make anything a PDF.