pdf-stamper.rb

require 'java'
require 'iText-2.1.3.jar'

module Java
  import 'java.io.FileOutputStream'
  import 'com.lowagie.text.pdf.PdfReader'
  import 'com.lowagie.text.pdf.PdfStamper'
  import 'com.lowagie.text.pdf.PdfWriter'
  import 'com.lowagie.text.pdf.BaseFont'
end

def stamp_pdf(src, target=nil, message=nil)
  include Java
  target ||= File.join(File.dirname(src), "#{File.basename(src, '.*')}-stamped.pdf")
  message ||= "JRuby + iText FTW!"
  
  reader = PdfReader.new(src)
  stamper = PdfStamper.new(reader, FileOutputStream.new(target))
  base_font = BaseFont.create_font(BaseFont::HELVETICA, BaseFont::WINANSI, BaseFont::NOT_EMBEDDED)
  page_count = reader.number_of_pages
  
  page_count.times do |i|
    page_num = i + 1 # itext uses 1-index page numbers...
    over = stamper.over_content(page_num)
    over.begin_text
    over.setFontAndSize(base_font, 25)
    over.setTextMatrix(100, 30)  # x, y location - bottom left = (0,0)
    over.show_text(message)
    over.end_text
    over.stroke
  end
  stamper.close
end

if __FILE__ == $0
  stamp_pdf(*ARGV)
end