LibreOffice is an open-source free alternative to heavy commercial office suites like MS Office. While having generally the same functionality, LibreOffice is more open to modification and updates, making it a more attractive suite if you want a comfortable and adjustable tool for working with documentation.
LibreOffice consists of several tools capable of working with documents of any type, from standard Word files and Excel tables to presentations and Publisher files. There's a word processing and desktop publishing tool called Writer; spreadsheet program Calc; tool for creating effective multimedia presentations called Impress; a sketching tool named Draw; database manager Base; formula editor Math; advanced chart and diagram creator Charts. Every tool has all the features of an advanced editor for the kind of files you could work with. The tools work stable and fast, they are easy to use even if you're not an experienced user of office tools.
LibreOffice adds several unique features into its programming, such as the support for ODT documents and the ability to incorporate various plugins and extensions. You can always add new templates for various documents.
Open-source tools sometimes disappoint by being attempts to copy a licensed product. LibreOffice is different in that, it's a genuinely good product itself.