PDF result certificates should not be considered official. You can verify the validity of a PDF certificate you receive in two ways:
1. Ask the test taker to share their result directly to your institutional dashboard via the Duolingo English Test website. This is the only official way for test takers to share their results.
2. Log into your institutional dashboard and navigate to the certificate link printed in orange at the top of the result certificate. You can then compare the certificate at the URL with the PDF certificate.