Scribus is an open-source multi-platform publishing program, working on Linux, BSD, Solaris, Mac OS X, Windows and others. It provides an intuitive, user-friendly interface, allowing users to easily publish their work.

It supports professional publishing features like color separations, CMYK and spot colors, ICC color management, and versatile PDF creation.
The latest unstable version available is Scribus 1.5.1 SVN , which is from the under-development branch.
Installation instructions:
The latest versions of Scribus are available via some third party PPA, so installing the software and keeping it up to date is a piece of cake.
All you have to do is add the PPA to your system, update the local repository index and install the scribus-trunk package:
$ sudo add-apt-repository ppa:scribus/ppa
$ sudo apt-get update
$ sudo apt-get install scribus-trunk
Optional, to remove scribus, do:
$ sudo apt-get remove scribus-trunk
The instructions are available for Ubuntu 15.10 Wily Werewolf, Ubuntu 15.04 Vivid Vervet, Ubuntu 14.04 Trusty Tahr and derivative systems: Linux Mint 17.x and Elementary OS 0.3 Freya.