Can I run Microsoft Office 2007 under Ubuntu?
How do I make ubuntu os run Microsoft office 2007 on my pc
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You can run MS Office on Wine (A Windows emulator). Wine is available in the software library for Ubuntu. http://www.winehq.org/download/ubuntu
If you have to run MS Office, Office 2007 is well-supported on CrossOver 11. I've had a lot less success with Office 2010, although it works well enough if you don't apply any of the service packs.
CrossOver is a commercially-supported version of WINE, so either one may work for you, but CrossOver handles a lot more of the application-specific tweaks for you. WINE is still the underling technology, of course, but requires a bit more hands-on fiddling to get various things to work properly.
As @minitech mentioned, LibreOffice will open and save Word's .DOC and .DOCX files. It's often a "good enough" solution, although complex formatting and platform-specific fonts may not always be perfectly preserved. As a concrete example, I've found that manual page breaks in LibreOffice can insert blank pages when viewed in MS Office. That's not really a huge deal, but it's the sort of formatting issue that makes WINE or CrossOver necessary if your target audience will be opening everything in Word.
Lastly, don't forget about pandoc and unoconv. I often use pandoc to convert Markdown or HTML documents to .DOCX files, and think it's an exceptionally good choice if you're authoring documents. Unoconv can convert to and from any format understood by LibreOffice, although it requires that LibreOffice be installed in order to work, and is really more of an automation tool than a solution for authoring documents.
You have a lot of choices here: commercial tools, free tools, and alternative applications. Pick whichever one fits your workflow best.