Yes on demo, we've defined two property groups, take a look there, click on a document and the icons of adding property group it'll be enabled.
Search engine runs too with property groups, enabling searching documents by this parameters.
You can add more property group, registering on admin option.
We've restored demo and forget to register property groups, I've done it this morning, you'll could see it.
See faq entry
http://www.openkm.com/FAQ.html there's an example of how to create property group files to register. There's are some entry too about it on forums but this is on spanish
http://www.openkm.com/Configuration/54-Configurar-Grupos-de-Propiedades.html