Keyframe pasting not available for grease Pencil

I would copy the kf of grase pencil on dopesheet\mode: grease pencil just as is described in this link

http://wiki.blender.org/index.php/Doc:2.6/Manual/3D_interaction/Sketching/Layers_and_Animation

instead of the window displays the following error message:

“keyframe pasting is not available for Grease Pencil mode”

how can I fix it?
can be copied the keyframes into another file blend?