www-gem

I used to use the famous Zathura for a long time, but it’s really minimal. Sioyek is an incredible pdf reader so overlooked.
Amongst a lot of other things, it lets you:

• quickly preview or jump to figures/references/equations/tables… (even if the PDF does not have links)
• search paper names in any search engine you like (defaults are google scholar and library genesis) by middle clicking on their name or using keybindings
• mark locations (using lower case for local mark and upper case for global mark) or create bookmarks for quick navigation
• highlight text
• save annotations in a local database or embed them in a new version of the PDF file to share them with others
• automatically reload a file when it changes

I wrote a brief overview of it quite some time ago.

Seems outside of what one would expect from a terminal. There’s dedicated app to handle this task.

Maybe you can find some inspiration here.