The Collaborative International Dictionary of English v.0.48:

Documental \Doc`u*men"tal\, a.
   1. Of or pertaining to instruction. [Obs.] --Dr. H. More.
      [1913 Webster]

   2. Of or pertaining to written evidence; documentary; as,
      documental testimony.
      [1913 Webster]

WordNet (r) 3.0 (2006):

documental
    adj 1: relating to or consisting of or derived from documents
           [syn: documentary, documental]