Hello,
I would recommend you to create duplicate fields to your document type, I mean document title field, document keywords field and document description field. Editor will fill them on the Form tab and you'll save them on button click to the document metadata fields using our 
API. This can be done in the 
~\CMSModules\Content\CMSDesk\Edit\Edit.aspx.cs file. Please focus on the 
SaveDocument method.
Hope this sheds some light.
Best regards
Ondrej Vasil