As you may know, MuPDF is a free, open-source, lightweight PDF viewer written in C, with all the basic features of any other PDF viewer and vim-like keybinds.

The latest version available is MuPDF 1.9, which has been recently released, coming with changes.
Headline changes:
- New command line tools: create and run.
- New low-level Java interface for desktop and android.
- Bidirectional layout for Arabic and Hebrew scripts.
- Shaping complex scripts for EPUB text layout.
- Noto fallback fonts for EPUB layout.
mutool create:
- Create new PDF files from scratch.
- Read an annotated content stream in a text file and write a PDF file, automatically embedding font and image resources.
mutool run:
- Run javascript scripts with MuPDF bindings.
- The interface is similar to the new Java interface.
mutool draw:
- Optional multi-threaded operation (Windows and pthreads).
- Optional low memory mode (primarily for testing).
Installation instructions:
The latest MuPDF builds are available via some third party PPA, so installing it on Ubuntu is easy. Just add the PPA to your system, update the local repository index and install the mupdf and mupdf-tools packages:
$ sudo add-apt-repository ppa:ubuntuhandbook1/apps
$ sudo apt-get update
$ sudo apt-get install mupdf mupdf-tools
Optional, to remove mupdf, do:
$ sudo apt-get remove mupdf mupdf-tools
The installation instructions should work on Ubuntu 16.04 Xenial Xerus, Ubuntu 15.10 Wily Werewolf, Ubuntu 14.04 Trusty Tahr, Linux Mint 17.x, Elementary OS 0.3 Freya and other Ubuntu derivative systems.