How to view properties of a PDF document opened in Chromium-based web browser?

Solution 1:

As a workaround, one can substitute Chromium PDF viewer with Mozilla's PDF.js via corresponding extension. In this case, by clicking Tools -> Document Properties... one can retrieve basic info:

There are few downsides I think worth mentioning:

• Overall performance is subjectively worse (even with enabled WebGL). Scrolling and scaling are slower, font rendering is somewhat choppy.
• Chromium's yellow tick marks on the scrollbar won't show up when searching the PDF document.
• Address bar is populated with an uninformative chrome-extention://... string instead of the actual URL.

Solution 2:

This can now be enabled in Chrome 89 and newer through chrome://flags/#pdf-viewer-document-properties (bug)