Somewhere on my website is a link to a .pdf which has been deleted. Its showing up on my SEO Moz account as a critical crawler issue, but i cant find the link to the .pdf anywhere on my site?

Moz is suggesting a link to a .pdf file is showing a 4xx error. Its shows the referring link page but i cant see anywhere on the page a link to the .pdf. 

Is there a way of searching for the link?

You might be able to find it using a Broken Link Checker tool. I'd use a few different ones, sometimes one of them picks up links others miss. Here are a few to get you started:

•  https://www.brokenlinkcheck.com/
• https://brokenlinkfinder.com/
• https://www.deadlinkchecker.com/