title: Open a pdf with blank password with pdftk
body: <p>We occasionally receive pdf files with blank/empty passwords. We use pdftk and under these circumstances it fails. We have tried:</p>
  
  <pre><code>pdftk input.pdf input_pw  output output.pdf
  pdftk input.pdf input_pw \ output output.pdf
  pdftk input.pdf input_pw '' output output.pdf
  pdftk input.pdf input_pw "" output output.pdf
  </code></pre>
  
  <p>All fail indicating that we have supplied an incorrect password, however this command works great when the password consists of actual characters. We were hoping that quotes or a \ escaping would trick it, but no love. We found a workaround with qpdf and are going to use that for now, but was hoping someone out there could crack this nut.</p>