Google’s John Mueller said in a webmaster hangout on YouTube that links in PDF files basically count as nofollow links:
“Within PDFs, there’s no way to let us know that a link is is really a link that you want to use to pass signals. We would generally view these links as text links that we also find in text files.
Essentially as similar to a nofollow linkm in that we recognize the link is there, we can look at where this link is pointing at, but for the most part we would not be forwarding any signals through those links.
So from a pure SEO point of view I would say it’s questionable that you had any advantage from this. But from a usability point of view, I would totally make sure you have those links within your PDFs.”
You can view the video here:
Check the links that point to your website
You can use the free link analysis tool OpenLinkProfiler.org to check the links that point to your website: