Step 1: Open the course with the file you want

Step 2: Click Modules on the left hand side

Step 3: Select the desired file

Step 4: Download the file

Step 5: Save the file to your downloads folder (By clicking and dragging)

Step 6: Launch Squid

Step 7: Click the plus in the bottom, right hand corner 

Step 8: Click "Import PDF"

Step 9: Find the file

Step 10: Start editing!