How do you edit the html/css headings for plugin divs?

Hello. I am trying to edit the html heading for the Document viewer once you click into an item record. Right now, its a H2 heading and I want it smaller, but I cannot find the file that I would edit to make that change. Would someone be able to share that file and its location please? I included a screenshot of what I want to edit.

Looks like it’s views/shared/common/docs-viewer.php

Thank you! Bit of an over site on my part. I thought I went through that file already but after you suggested it, I looked and found it. I must have skipped the common and just checked the other two above common. Thank you for the quick response and help!