The NAF header has two elements for this: fileDesc and public:
fileDesc provides metadata about the naf document itself (filename, creation date, etc.)
public provides public information about the document, like an URI. The information provided there is minimal indeed, and publication date for instance is not supported.
The attributes for these elements can be found in the DTD
What is the recommended way to store document metadata in NAF? For instance the file name and/or URI of the document being processed.
Also interesting could be author, publication date, creation date, etc.