Cannot read properties of null (reading ‘ShadowRoot’) – Java and Selenium

I am trying to web scrape using Java and Selenium but for one part of what I need to web scrape, it requires me to access a shadow DOM element. I am using Javascript executor to access it and I am entering the querySelector snippet needed to retrieve what I am looking for but I am getting a “Cannot read properties of null (reading ‘ShadowRoot’)” error. Is anyone familiar with this and how to solve it?

Here is my code snippet:

 String pagePdfUrl = (String) js.executeScript("document.querySelector('pdf-viewer').shadowRoot.getElementById('content').querySelector('embed').getAttribute('original-url')");

js is the JavascriptExectuor variable.

Thank you!