Annotate PDF with stylus

How to annotate a PDF

sudo apt-get install okular

Open the PDF with Okular, press Review, then go to Settings → Full Screen Mode (or ctrl + shift + F). You can close full screen mode by pressing the combination again, but in case you can't remember it: Press alt to open the HUD, type "exit", and press enter.

You might want to define different free hand pencils in the settings. (I have no idea how well they work with a stylus since I don't have one, but there is still the other option using LibreOffice.)

How to import PDFs into LibreOffice Impress

Open any LibreOffice Module or the LibreOffice starter and choose File → Open. Select the PDF. LibreOffice Draw will open. Select any slide on the left and press ctrl + A to select all of them. Copy them, open up LibreOffice Impress, and paste them in the slide panel there. Start your presentation by choosing Slide Show → Start From First Slide or pressing F5.

You could use xournal. (sudo apt-get install xournal) It can open a pdf as background and you can write, paint, mark and annotate.