I installed qpdfview and liked it more than Evince. So I want to remove Evince. Is it advisable (as it is a core item in Ubuntu 14.04)?
In your case, the program Evince was installed on your system as a component of the ubuntu-desktop metapackage. There are several excellent answers here about what a metapackage is and the implications of uninstalling a component of a metapackage and the metapackage itself. Here are two:
Coming back to your case, if you run
apt-cache show ubuntu-desktop and examine the output, you'll see a section called Depends:. This lists all the software, including Evince, specified by the ubuntu-desktop metapackage. If you attempt to uninstall any of the packages in that list, the ubuntu-desktop metapackage will also be uninstalled (along with other dependencies unique to the package you want to uninstall in the first place).
Going further down, you'll see this:
Description-en: The Ubuntu desktop system This package depends on all of the packages in the Ubuntu desktop system . It is also used to help ensure proper upgrades, so it is recommended that it not be removed.
In other words, sometime in the future, when you want to upgrade your system to the next permissible version of Ubuntu, the upgrade process will want to refer to the ubuntu-desktop metapackage. At that time, it will be advisable that you re-install ubuntu-desktop before undertaking the upgrade step. Until that time, not having ubuntu-desktop on your system doesn't mean you'll be without a "desktop"; its absence has no adverse day-to-day consequences.
As a precaution, the next time you want to uninstall anything, run a simulation first by leaving out
sudo and by including
-s. For a really scary simulation, look at the output of
apt-get purge -s zenity. Then, if you have doubts, you could research the matter as you did for Evince!