Moodle has an integrated grading system which allows you to review submitted assignments, annotate them (comments, drawing, highlighting), and grade them all from the Moodle site, without requiring you to actually download any files to your computer.
In order for this to work properly, you should consider limiting assignment submissions to PDF files as PDFs can be viewed directly inside of Moodle unlike Word/Powerpoint/etc which would have to be downloaded to your computer first. All modern software should be able to save files as PDFs.
In the assignment setup within Moodle, you simply add “.pdf” in the “Accepted file types” area:
See the video below for how to grade and provide feedback on these kind of assignments: