If you install the new version, it will not overwrite the old one, because each version uses its own folder, usually with a name of the form
/opt/MATLAB/. The same holds for the settings, which are kept in a folder of the same name under
~/.matlab/. This way it is possible to use in parallel two or more different versions of Matlab.
matlab is usually a symbolic link in
/usr/local/bin/ which points to the actual binary, e.g.
/usr/local/bin/matlab -> /opt/MATLAB/R2013a/bin/matlab
If you want to start another version, you have to type the full pathname of the executable at the command line, e.g.
If you only want to use the new version though, I'd recommend to uninstall the old version first. Uninstallation is done by deleting the installation directory with all its contents, and all the symbolic links pointing into that directory in
matlab, there can be e.g.
mex or links to other executables. The link you provided says essentially the same, except for additional information on (de-) activating a Matlab license.