diff --git a/cpdfcommand.ml b/cpdfcommand.ml
index 34db148..90072d8 100644
--- a/cpdfcommand.ml
+++ b/cpdfcommand.ml
@@ -404,6 +404,9 @@ let spray_outputs = ref []
 (* A list of PDFs to be output, if no output method was specified. *)
 let output_pdfs : Pdf.t list ref = ref []
 
+let standard_namespace = "http://iso.org/pdf/ssn"
+let pdf2_namespace = "http://iso.org/pdf2/ssn"
+
 type font =
   | StandardFont of Pdftext.standard_font
   | EmbeddedFont of string
@@ -1885,6 +1888,11 @@ let setreplaceobj s =
   | [a; b] -> args.op <- Some (ReplaceObj (a, b))
   | _ -> error "replace_obj: bad specification"
 
+let expand_namespace = function
+  | "PDF" -> standard_namespace
+  | "PDF2" -> pdf2_namespace
+  | x -> x
+
 let specs =
    [("-version",
       Arg.Unit (setop Version),
@@ -2813,6 +2821,7 @@ let specs =
    ("-artifact", Arg.Unit (fun _ -> Cpdfdrawcontrol.artifact ()), " Begin an artifact");
    ("-end-artifact", Arg.Unit (fun _ -> Cpdfdrawcontrol.endartifact ()), "End an artifact");
    ("-no-auto-artifacts", Arg.Unit (fun _ -> Cpdfdrawcontrol.autoartifacts false), " Don't mark untagged content as artifacts");
+   ("-namespace", Arg.String (fun s -> Cpdfdrawcontrol.addnamespace (expand_namespace s)), " Set the structure tree namespace");
    ("-rect", Arg.String Cpdfdrawcontrol.addrect, " Draw rectangle");
    ("-to", Arg.String Cpdfdrawcontrol.addto, " Move to");
    ("-line", Arg.String Cpdfdrawcontrol.addline, " Add line to");
diff --git a/cpdfdraw.ml b/cpdfdraw.ml
index d4f68dc..6466196 100644
--- a/cpdfdraw.ml
+++ b/cpdfdraw.ml
@@ -64,6 +64,7 @@ type drawops =
   | EndSTag
   | BeginArtifact
   | EndArtifact
+  | Namespace of string
 
 (*let rec string_of_drawop = function
   | Qq o -> "Qq (" ^ string_of_drawops o ^ ")"
@@ -238,6 +239,11 @@ let mcidr = ref ~-1
 let mcid () = (incr mcidr; !mcidr)
 let mcpage = ref ~-1
 
+let standard_namespace = "http://iso.org/pdf/ssn"
+let pdf2_namespace = "http://iso.org/pdf2/ssn"
+
+let namespace = ref standard_namespace 
+
 (* The structure data, as it is created, in flat form. Later on, this will be
    reconstructed into a structure tree. *)
 type structdata =
@@ -429,6 +435,7 @@ let rec ops_of_drawop struct_tree dryrun pdf endpage filename bates batespad num
   | EndSTag -> if not dryrun then structdata =| StDataEndTree; []
   | BeginArtifact -> [Pdfops.Op_BMC "/BeginArtifact"]
   | EndArtifact -> [Pdfops.Op_BMC "/EndArtifact"]
+  | Namespace s -> if not dryrun then namespace := s; []
 
 and ops_of_drawops struct_tree dryrun pdf endpage filename bates batespad num page drawops =
   flatten (map (ops_of_drawop struct_tree dryrun pdf endpage filename bates batespad num page) drawops)
diff --git a/cpdfdraw.mli b/cpdfdraw.mli
index 8844f48..4e8b156 100644
--- a/cpdfdraw.mli
+++ b/cpdfdraw.mli
@@ -59,6 +59,7 @@ type drawops =
   | EndSTag
   | BeginArtifact
   | EndArtifact
+  | Namespace of string
 
 val do_add_artifacts : bool ref
 
diff --git a/cpdfdrawcontrol.ml b/cpdfdrawcontrol.ml
index 883f8d7..b22ac5d 100644
--- a/cpdfdrawcontrol.ml
+++ b/cpdfdrawcontrol.ml
@@ -119,6 +119,9 @@ let artifact () =
 let endartifact () =
   addop Cpdfdraw.EndArtifact
 
+let addnamespace s =
+  addop (Cpdfdraw.Namespace s)
+
 let addrect s =
   let x, y, w, h = Cpdfcoord.parse_rectangle (Pdf.empty ()) s in
     addop (Cpdfdraw.Rect (x, y, w, h))
diff --git a/cpdfdrawcontrol.mli b/cpdfdrawcontrol.mli
index dac3f48..e0036e0 100644
--- a/cpdfdrawcontrol.mli
+++ b/cpdfdrawcontrol.mli
@@ -19,6 +19,7 @@ val addstag : string -> unit
 val endtag : unit -> unit
 val endstag : unit -> unit
 val autotags : bool -> unit
+val addnamespace : string -> unit
 val artifact : unit -> unit
 val endartifact : unit -> unit
 val autoartifacts : bool -> unit