```ruby
class Pdftk < BaseCustom
  def path
    "#{build_path}/vendor/#{name}"
  end
  def name
    "pdftk"
  end
  def source_url
    "http://s3.amazonaws.com/source_url_here"
  end
  def used?
    File.exist?("#{build_path}/bin/pdftk") && File.exist?("#{build_path}/bin/lib/libgcj.so.12")
  end
  def compile
    write_stdout "compiling #{name}"
    #download the source and extract
    %x{ mkdir -p #{path} && curl --silent #{source_url} -o - | tar -xz -C #{path} -f - } 
    write_stdout "complete compiling #{name}"
  end
  def cleanup!
    
  end
  def prepare
    File.delete("#{build_path}/bin/lib/libgcj.so.12") if File.exist?("#{build_path}/bin/libgcj.so.12")
    File.delete("#{build_path}/bin/pdftk") if File.exist?("#{build_path}/bin/pdftk")
  end
  
end```

Add pdtkf source S3 url
user
```ruby
class Pdftk < BaseCustom
  def path
    "#{build_path}/vendor/#{name}"
  end
  def name
    "pdftk"
  end
  def source_url
    "https://s3-eu-west-1.amazonaws.com/opg-lpa-test/pdftk.tar.gz"
  end
  def used?
    File.exist?("#{build_path}/bin/pdftk") && File.exist?("#{build_path}/bin/lib/libgcj.so.12")
  end
  def compile
    write_stdout "compiling #{name}"
    #download the source and extract
    %x{ mkdir -p #{path} && curl --silent #{source_url} -o - | tar -xz -C #{path} -f - } 
    write_stdout "complete compiling #{name}"
  end
  def cleanup!
    
  end
  def prepare
    File.delete("#{build_path}/bin/lib/libgcj.so.12") if File.exist?("#{build_path}/bin/libgcj.so.12")
    File.delete("#{build_path}/bin/pdftk") if File.exist?("#{build_path}/bin/pdftk")
  end
  
end
```
assistant