Many Linux (and BSD) versions have their own package managers built in and do not require you to touch the source files or use PPA files.
For example, with Linux Mint there is the "Software Manager" which has tens of thousands of applications that can be installed with a few clicks.
I have used PPA's for a few programs, but were possible I use the Software Manager.
I don't use Ubuntu or Kubuntu, but I believe there is "Software Centre" which is used to install applications. There should be no need to touch a PPA with that either.
In order to keep Linux Mint up-to-date, there is "Update Manager" which sits in the desktop panel and will tell you when something needs to be updated. I'm guessing Kubuntu would have something like this too.
Edit: If you want the "bleeding edge" or "very latest version" of a certain software application the day it is released you may need to follow the PPA, but that is not always the case. In most cases, the tested version that is installed using the package manager will be updated through the package management system. There is often very little need to have the very latest version on the day of release as well - at least for me :]
For example, Firefox is updated (on Linux Mint) through the Software Manager and the updates follow the main branch very closely.