Post form submit - open message in separate tab to PDF?

hi all, is there code to make the post-submit Thank You message appear in a separate tab to the Redirect (which opens tab with a PDF brochure)? At the moment the message appears for a split second and then disappears as the PDF brochure tab opens. I would like to have more information in the message for the client to read as well as having the brochure in a separate tab. Thanks. Simon

You mean when users enter the form >> show a message + open a pdf in a new tab?

Yes exactly - I would like to display a message and open a PDF in a new tab. At the moment the message appears and then instantly disappears as the PDF opens in the same tab.

In post form message >> Enter this code to HTML box

<p>enter your message text here</p>
<script>
  window.open('http://stackoverflow.com', '_blank');
</script>

Replace stackoverflow with your pdf url