demo.rb

class Demo < Prawn::Document
  def flower
    0.step(270, 90) do |angle|
      rotate(angle, :origin => [100, 100]) do
        fill_color(random_color)         
        polygon [100, 100], [150, 150], [200, 100]
        fill_and_stroke
      end
    end
  end

  def flower_chain
    4.times do |i|
      translate(100*i, 100*i) do
        flower
      end
    end
  end

  def flower_cross
    flower_chain

    rotate_around_center(90) do
      flower_chain
    end
  end

  def random_color
    rgb2hex([rand(255), rand(255), rand(255)])
  end

  def rotate_around_center(angle, &block)
    rotate(angle, :origin => [bounds.width/2, bounds.height/2], &block)
  end

  def text_wall
    float do
      text_box "The rain in Spain falls mainly on the plains. "*200,
               :align => :justify, :size => 9
    end
  end

  def prawn_banner
    transparent(0.2) do
      fill_rectangle bounds.top_left, bounds.width, bounds.height
    end

    transparent(0.75) do
      font("Courier", :size => 70, :style => :bold) do
        formatted_text [ { :text => "P R", :color => "000000" }, 
                         { :text => " A ", :color => "ff0000" },
                         { :text => "W N", :color => "000000" } ], 
                           :valign => :center,
                           :align  => :center
      end
    end
  end

  def github_sidebar
    rotate(90, :origin => [475,300]) do
     fill_rectangle [350,300], 150, 25
     fill_color "ffffff"
     text_box "github.com/sandal/prawn", :at => [350,300], :width => 150, :height => 25, 
                                         :valign => :center, :align => :center
    end
  end

end

Demo.generate("awesome.pdf", :page_size => [500,500], :margin => 0) do
  text_wall
  flower_cross
  github_sidebar
  prawn_banner
end

Nice demo. It might be worth noting that the rendered pdf output can be found at http://majesticseacreature.com/prawn-sample.pdf (as mentioned here)

link is down