def <<(object)
            owner = object.document

            #
            # Does object belongs to another PDF ?
            #
            if owner and not owner.equal?(self)
                import object
            else
                add_to_revision(object, @revisions.last)
            end
        end
def <<(object)
            owner = object.document

            #
            # Does object belongs to another PDF ?
            #
            if owner and not owner.equal?(self)
                import object
            else
                add_to_revision(object, @revisions.last)
            end
        end
Adds a new object to the PDF file.
 If this object has no version number, then a new one will be automatically
 computed and assignated to him.

 It returns a Reference to this Object.
 _object_:: The object to add.