Office work can be serious business, and for years there's been one premier free office suite: Open Office. Lately, the Open Office brand has given way to the more internationally-inclusive name Libre Office; a branding change that has not only strengthened the office suite but brought along an alliance of backers called the Document Foundation.
Install Libre Office with Add/Remove Software in the Activities Overview. Search for "libreoffice" with no spaces, for the best results.
Libre Office installs a full office suite:
If you're familiar with other office suites, then you'll ease right into Libre Office. The principles are the same and most of the workflow is the same as well. Libre Office, like any full-featured office suite, has extensive documentation if you need to learn all of its advanced functions.