29: def to_s
30: res = "\n#{@oid} 0 obj\n<< /Type /Catalog"
31: res << "\n/Outlines #{@outlines.oid} 0 R" unless @outlines.nil?
32: res << "\n/Pages #{@pages.oid} 0 R" unless @pages.nil?
33: res << "\n/ViewerPreferences #{@viewer_preferences.oid} 0 R" if @viewer_preferences and @parent.version >= '1.2'
34: res << "\n/OpenAction #{@open_here.oid} 0 R" unless @open_here.nil?
35: res << "\n/PageMode /#{@page_mode}" unless @page_mode.nil?
36: res << "\n/Version /#{@parent.version}" if @parent.version >= '1.4'
37: res << ">>\nendobj"
38: end