title: PDF Tm operator
body: <p>I'm trying to highlight text in a PDF document but I found a Tm operator with the following operands:</p>
  
  <pre><code>0 7.98 -7.98 0 90.8898 715.4183 Tm
  </code></pre>
  
  <p>The Tm operator is supposed to replace the text matrix and the text line matrix solely on its operands. 
  According to the Pdf Reference, the following operations can be done:</p>
  
  <ul>
  <li>Translations [1 0 0 1 tx ty]</li>
  <li>Scaling [sx 0 0 sy 0 0]</li>
  <li>Rotation [cos(angle) sin(angle) -sin(angle) cos(angle) 0 0]</li>
  <li>Skew [1 tan(alpha) tan(beta) 1 0 0]</li>
  </ul>
  
  <p>The format of the operands doesn't match any of the above transformations, which led to the following questions. </p>
  
  <ul>
  <li>What is the previously mentioned text matrix supposed to do? </li>
  <li>How would a several transformations look like? For example Scaling and rotation.</li>
  </ul>