DocHub is an extension that works in Google Drive that allows users to annotate a PDF either by typing or drawing. This can be used to facilitate a more "paperless" classroom where the students can complete and submit work digitally. It is already installed for the students.
From the teacher perspective, all you need to do is add the pdf file when you create a Classroom assignment and choose "Each student will get a copy." (If you have your worksheet in paper form, you can use the Scan function on the copy machine to email yourself a pdf version).
From the student perspective, there is an extra step to opening and an extra step to saving their work, but it really isn't too complicated. We have a video tutorial that demonstrates how to do it. I have linked it below for your reference, and I have posted it for all of the students under the Resources topic in their Tech Class on Google Classroom. You could also demonstrate the steps together in class for the first time you are asking them to use DocHub to complete a pdf worksheet to ensure everyone understands what to do.