title: What does "Not LTV-enabled" mean?
body: <p>I'm using iText 5.5.3 to sign and timestamp PDF documents. It works very well. But I recently switched from Acrobat Pro X to XI and now I see this new line :</p>
  
  <pre><code>the signature is not LTV enabled and will expire after &lt;date&gt;
  </code></pre>
  
  <p>I guess this warns me that after this date, the signer's signature will be seen as invalid, right ? However the signature properties tells me :</p>
  
  <pre><code>the signature includes an embedded timestamp : &lt;date/time&gt;
  signature was validated as of the secure timestamp time : &lt;same date/time&gt;
  </code></pre>
  
  <p>Now I'm a little bit confused : since the signature was declared valid at a known and certified date, why would it become invalid in the future ?</p>