This pair of code-bits convert a PDF to plain text using the ancient pdftotext library.

document.rb

#models/document.rb
class Document < ActiveRecord::Base
  has_attached_file :pdf,:styles => { :text => { :fake => 'variable' } }, :processors => [:text]
#more class stuff here
end

text.rb

#lib/paperclip_processors/text.rb
module Paperclip
  # Handles extracting plain text from PDF file attachments
  class Text < Processor

    attr_accessor :whiny

    # Creates a Text extract from PDF
    def make
      src = @file
      dst = Tempfile.new([@basename, 'txt'].compact.join("."))
      command = <<-end_command
        "#{ File.expand_path(src.path) }"
        "#{ File.expand_path(dst.path) }"
      end_command

      begin
        success = Paperclip.run("/usr/bin/pdftotext -nopgbrk", command.gsub(/\s+/, " "))
        Rails.logger.info "Processing #{src.path} to #{dst.path} in the text processor."
      rescue PaperclipCommandLineError
        raise PaperclipError, "There was an error processing the text for #{@basename}" if @whiny
      end
      dst
    end
  end
end