Evince vs. Atril
Linux Lite uses GNOME's Evince document viewer, with its clunky "CSD" combined titlebar-cum-toolbar, while MATE's Atril, with a more traditional UI, was right there in the repositories.
Having used both, (for me) there is something that makes me put up with Evince's CSD... ...which, disclaimer, I'm not wild about: last time I compared the two, Evince has the better search and presentation of search results. If Atril would bring it up to the same standard I would switch in a heartbeat. But having to work with large pdfs professionally a lot, and the main use case being to search for the relevant passages, Evince has the clear advantage (for me). So yeah, there is more... which makes you put up with CSD ;)