While subbing, I learned of this app called Notability. The district has a paid subscription for students to use on their devices, and it's saved so many trees! Students can edit PDFs their teacher shares with them. Instead of printed copies of worksheets and note sheets, students write directly on them and submit their work to their teachers. I have not yet explored whether it can be used on secured PDFs, but I believe so. If you know, can you comment below? The free account is limited but worth exploring if your students are one-to-one with devices.
I'm just a science teacher sitting at my computer generating and finding ideas to make learning more enjoyable.