I think the main idea of this tread is "render encrypted pdf document on user side".

But all this is literally "back to flash/java applets era" 2000-2010 of Web technology.

Back then there were many popular websites that render itself on Java-applet or Flash-applet... it was absolutely horrible user experience even back then.

Now we have way too many "devices" to support in your custom "web render" - only huge corporations with unlimited money can support this many platforms at once in custom render.

I know large corporations these days develop some complex WASM+WebGPU solutions that complexity on impossible level (to make it protected from user impact on content or rendering).

P.S> in reality - Webbrowser are very broken piece of software, and rendering something more complex than "html file with simple css style" usually leads to "horrible user experience", Canvas implementation is broken...it just "exploding complexity" problem that leads to discovering bugs in everything (OS/CPU/RAM/BIOS/etc).... short - technology is not ready, modern consumer computer technics(and software) is "ultra broken" on every level possible (drivers/hardware/software).