I have a pdf file liked to page. This can be downloaded.
<a rel="noopener" target="_blank" title="opens in new window" href="https://example.com/files/CertainTeed_ASNZS4020_PASS.PDF">Sample Certificate</a>
GSE is telling me
Page Indexing Issue
Duplicate without user-selected canonical
How can I stop it from thinking that it's a webpage ? I am thinking of adding a nofollow to the rel attribute