As you may know, Diodon is a lightweight clipboard manager for Gnome and Unity, with support for the Ubuntu indicator. Also, it has a clipboard sync feature, the key combinations can be changed by the users and has a customizable size.
The latest version available is Diodon 1.4, which brings new features. For usage instructions, see this article.
The latest version of the software is available via some third party PPA, so you should not encounter too many problems when installing the software on your Ubuntu system.
All you need to do is add the PPA to your system, update the local repository index and install the diodon package:
$ sudo add-apt-repository ppa:diodon-team/stable
$ sudo apt-get update
$ sudo apt-get install diodon
Also, the Unity users can install the diodon scope, with the below command:
$ sudo apt-get install unity-scope-diodon
Optional, to remove diodon, do:
$ sudo apt-get remove diodon unity-scope-diodon
The installation instructions should work on Ubuntu 15.10 Wily Werewolf, Ubuntu 15.04 Vivid Vervet, Ubuntu 14.04 Trusty Tahr, Linux Mint 17.x, Elementary OS 0.3 Freya and other Ubuntu derivative systems.