On chrome and firefox you’ve the option to view just the frame on the page by right clicking and selecting view frame only. This feature is useful as often if a frame is displaying a pdf can make it difficult to read as the size of the frame can make the document quite small depending on the screen size. Full screen can be used but this means you’ve to exit full screen every time you need to view another tab then re-enter full screen when you want to view the document again.
Amazingly you can view the “Frame Source” but can’t view the contents of the frame in a separate tab. This is an important feature for website developers.