Google Drive is a professional alternative to Microsoft or Open Office. It is free as long as you do not use too much space. It is simple to use. You just need a Google account to open a new document to collaborate on even synchronously.
A basic alternative would be e.g. Titanpad. This only gives you the option to edit text together. Further information at https://effectivewebinars.wordpress.com/titanpad/
Effective Webinars 