pdf_merger.rb

class PdfMerger
  
  def merge(pdf_paths, destination)
    
    first_pdf_path = pdf_paths.delete_at(0)
    
    Prawn::Document.generate(destination, :template => first_pdf_path) do |pdf|
      
      pdf_paths.each do |pdf_path|
        pdf.go_to_page(pdf.page_count)
        
        template_page_count = count_pdf_pages(pdf_path)
        (1..template_page_count).each do |template_page_number|
          pdf.start_new_page(:template => pdf_path, :template_page => template_page_number)
        end
      end
      
    end
    
  end
  
  private
  
  def count_pdf_pages(pdf_file_path)
    pdf = Prawn::Document.new(:template => pdf_file_path)
    pdf.page_count
  end
  
end