title: Paperclip- validate pdfs with content_type='application/octet-stream'
body: <p>I was using <code>paperclip</code> for file upload. with validations as below:</p>
  
  <p><code>validates_attachment_content_type :upload, :content_type=&gt;['application/pdf'],
                                     :if =&gt; Proc.new { |module_file| !module_file.upload_file_name.blank? },
                      :message =&gt; "must be in '.pdf' format"</code></p>
  
  <p>But, my client complained today that he is not able to upload <code>pdf</code>. After investigating I come to know from request headers is that the file being submitted had <code>content_type=application/octet-stream</code>. </p>
  
  <p>Allowing <code>application/octet-stream</code> will allow many type of files for upload.</p>
  
  <p>Please suggest a solution to deal with this. </p>