Você pode usar apt-get install para fazer o que quiser. O apt-get manpage diz o seguinte:
This is also the target to use if you want to upgrade one or more already-installed packages without upgrading every package you have on your system. Unlike the "upgrade" target, which installs the newest version of all currently installed packages, "install" will install the newest version of only the package(s) specified. Simply provide the name of the package(s) you wish to upgrade, and if a newer version is available, it (and its dependencies, as described above) will be downloaded and installed.
Se você deseja instalar uma versão conhecida de um pacote, também é possível especificar isso na linha de comando.
apt-get install apache2=2.2.14-5ubuntu8.3