I want to be able to customise the UI when embedding a PDF

When you embed a PDF in a web page today — whether via an <iframe>, <embed>, or <object> element — the browser renders it using its own native PDF viewer. The problem is that this viewer looks and works differently across browsers, and it is not customisable. If I need consistent, branded, or simplified UI around the PDF, I have no choice but to ship a full third-party PDF renderer like PDF.js with my application, adding significant weight to my codebase.

I want a standardised way to control the PDF viewing experience when browsers already have PDF rendering capabilities. For example, I should be able to:

• Suppress the browser's default toolbar entirely so I can provide my own controls.
• Enable or disable specific built-in features (e.g., download, print, page navigation).
• Supply a custom UI shell, similar to how the Window Controls Overlay API allows PWA chrome customisation.

This would allow developers to deliver a polished, accessible, and consistent PDF experience without duplicating what the browser already knows how to do.