A PDF reader under steroids: sioyek

For years, zathura has been my PDF reader of choice. I liked it simplicity, efficiency, clean look, and customization. I could see very few features missing but there were ways to workaround that and no other PDF reader was able to offer me the same pleasant experience. That was true until I came across sioyek .
Being focused on textbooks and research papers, it brings some very interesting features that may even appeal to people who are simply looking for a way to make their PDF navigation more efficient, especially when jumping to/from tables (more on that later).

A demo worth a thousand words and there is an excellent one provided by the developer him/herself:

╭── Overview of some features

The exhaustive list of all the features would be too long so here are some that stand out in comparison to other PDF readers:

• 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. You can assign one search engine to any single letter, so technically you could have up to 26 different search engines
• Searchable table of contents
• Using portals: sioyek will open a new window and automatically show the figure/table mentioned in the current paragraph as you go so you don’t have to jump back and forth. You can also decide to create your own portals, even from one file to another to create cross referenced for example.
• Browser-like history navigation
• Mark locations (using lower case for local mark and upper case for global mark) or create bookmarks for quick navigation
• Searchable highlights/bookmarks
• Visual ruler to highlight the line currently being read. It reduces eye strain and allow jumping to/preview figures/references/equations/tables… without needing to click on the reference.
• Highlight text
• Save annotations in a local database or - to share them with others - embed them in a new version of the PDF file (with the embed_annotations command). You can also export all your data (including bookmars and highlights) into a json file.
• Automatically reload a file when it changes
• List of recent documents for quick opening

Note that sioyekdoes not have tabs and relies on the recent documents access. If you really want tabs, you may use tabbed.

╭── Endless customization

Like any good app in Linux, you can change all the keybindings of sioyekusing the keys_user.config file.
Type “:” to access to a full searchable list of the commands.

But you can also adjust the entire behavior of this reader to your needs/liking using the prefs_user.config file. Here is mine to give you an infinitecimal overview of what you can do:

# launch sioyek in a new window (you can also chose a new instance)
should_launch_new_window 1

# automatically change the colors on startup and activate smooth scroll
startup_commands toggle_custom_color;toggle_smooth_scroll_mode

# change the background color
custom_background_color #333333

# auto adjust the zoom on startup
fit_to_page_width_ratio 0.5

# sioyek will try to create a table of contents if the document doesn't have one
create_table_of_contents_if_not_exists 1
max_created_toc_size 5000

# search options
super_fast_search 1
case_sensitive_search 0

# change highlights colors
highlight_color_b #00b4ff
highlight_color_g #27ff0a
highlight_color_r #ff0000
highlight_color_h #fff00a

# position and size of the overview window to quickly see figures/references/equations/tables...
overview_size 0.7 0.7
overview_offset 0 0 

# change the ruler properties
visual_mark_color 0.0  0.0  0.0  0.3
ruler_mode 1
ruler_padding 1.0
ruler_x_padding 5.0

# change the search engine to look for references
search_url_p https://pubmed.ncbi.nlm.nih.gov/?term=

Icing on the cake, sioyek offers a great documentation to help you taking the control very easily.

╭── Missing a feature?

You can extend sioyek using external commands and scripts. Some of them are already available here and offer OCR, translation, text-to-speech.
If you know how to write a script, the sky is the limit. The documentation also provides you with everything you need to know.