A comment on pdf annotation on unix systems. Go to the link for follow-up links to spacemacs and the layer in question:

Zathura is amazing, but if you want to take notes in a more or less zathura style pdf-editor (more than just reader), then I would recommend you to check out Spacemacs with its pdf layer. It has all features that Zathura has, but it adds very strong annotation features, it is mind blowing. You have a pdf-editor right within your vim-like editor. With org-noter you can send annotations directly to your org files (the video uses Emacs bindings, but the Spacemacs project uses a perfect Vim rebuild within Emacs). Spacemacs additionally comes with the amazing org-mode for organizing your notes. Due to the Spacemacs layer system, it is very easily installed (I assume you are on a GNU/linux type of system, as you are already using Zathura). There even exists an option to highlight using the keyboard only, although in this case I find it easier to use the mouse.