As you may know, QCAD is an open source 2D CAD (computer aided drafting) application that helps the users create technical drawings. Being multi-platform, it works on Linux, Mac OS X and Windows.
The latest version available is QCAD 3.21.3, which has been released a recently.There is an open-source version for the community and a paid version, which can be bought from here. The version from the PPA comes with the addon disabled by default.
Due to the fact that it is available via PPA, installing qcat on Ubuntu 18.10 Cosmic Cuttlefish, Ubuntu 18.04 Bionic Beaver, Ubuntu 16.04 Xenial Xerus, Linux Mint, Elementary OS and other Ubuntu based systems, the installation steps are quite straight-forward.
All you need to do is add the PPA to your system, update the local repository index and install the qcad package:
$ sudo add-apt-repository ppa:alex-p/qcad
$ sudo apt-get update
$ sudo apt-get install qcad
Optional, to remove qcad, do:
$ sudo apt-get remove qcad