Answer to your question and method for figuring out other "how to do something ubuntu in debian" questions. A great way to answer a lot of these questions is simply use `apt-cache search` however this is not always enough. The next thing to try is apt-file. Install apt-file:

  # apt-get -y install apt-file

Update apt-file db (might do this on install, I forget):

  # apt-file update

Now the bit you are interested in: How do you add PPAs in ubuntu? Answer: `add-apt-repository`

Does debian have something named add-apt-repository?

  # apt-file search add-apt-repository
  software-properties-common: /usr/bin/add-apt-repository
  software-properties-common: /usr/share/man/man1/add-apt-repository.1.gz

That looks familiar.

  # apt-get install -y software-properties-common 
  # add-apt-repository ppa:libreoffice/ppa

As a long time debian fanboy I have to say "new software is exclusively published on Ubuntu" was kind of funny. Unless you were talking about `upstart` ;) A great reseource for debian is the Debian Administrators Handbook. The section on pinning is:

http://debian-handbook.info/browse/stable/sect.apt-get.html#...