The properties of a document can be exported as metadata on an HTML page easily.

To enable the rendering as metadata, add some Velocity statements to the 'Main Layout'.

#if ($projectdocContext)
${projectdocContext.toHtml($sitemeshPage)}
#end

To add the snippet, follow the following steps:

1. As admin user, select 'Layout' in the 'General configuration'
   Image Added
2. Then click 'Create custom' (if you have not already applied changes to the layout) or 'Edit' (if there are already changes to the default provided by Confluence)
   
3. Finally add the above snippet after the rendering of the meta elements
   
4. Save the changes