Someone sent me a marriage file typed in .odt format.
I had never heard of this one, so asked around and got some helpful info.
1) Go here: http://www.officeviewers.com/ and download TextMaker Viewer. Its
free and opens all kinds of documents. (I did this one since it seemed so simple, and also because I get all sorts of formats sent to me!)
2) You can try this:
http://www.openoffice.org/
This page explains it more fully.
http://filext.com/file-extension/ODT
I didn’t actually download this one — but it is a very good explanation of this new type of software.