update version

I am curious as to how to correctly update the version as exposed by the api call in:

http://writer.zoho.com/public/help/postsavedoc/fullpage

At first glance I thought this was similar to the "upload document" functionality in that a document could be uploaded to replace the version. However, it asks for raw content data, but does not specify the format. I was able to upload plain content (e.g. the string "asdf"), but when I send MS Word formatted content, it does not work correctly (i.e. the contents of the file are garbled). What is the intended use of this call?