thanks.. can you make it work for pdf files viewed in firefox too? also it seems it is not working on the addons website itself (at least not right now for me)

Worked just fine for a couple months, then Firefox quarantined it (when it was still named Dark Mode and wasn't recommended yet), this message appears below the disabled and locked out "Dark Mode" :
Dark Theme (Malware) has been blocked for your protection.

Why was it blocked?
This add-on violates Mozilla's ad-don policies by using obfuscated code.
What does this mean?

The problematic add-on or plugin will be automatically disabled and no longer usable.
When Mozilla becomes aware of add-ons, plugins, or other third-party software that seriously compromises Firefox security, stability, or performance and meets certain criteria, the software may be blocked from general use. For more information, please read this support article.

Blocked on Feb 28, 2020. View block request.
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Now I'm using the slightly inferior Dark Night Mode add-on, because I can't stand all that LED light at night, especially that harmful blue wave we experience that seriously messes with the circadian rhythm/sleep cycle (like those new LED streetlights, im glad my city still mostly just has the orange sodium lights and hope the newfound harmful health effects slow down the deployment of that even worse light pollution).

Mr. Shutau, can I trust your new "Dark Reader" or will it attempt to inject malicious code sometime in the future? I really liked your "Dark Mode", but using Debian Linux, I was surprised to see the word Malware in my add-ons when I went to the Add-Ons menu when I noticed the extension stopped working and the icon disappeared from my toolbar.

If an explanation of what happened here can be obtained, I'd love to see it...

Looks good but a tad heavy and contrast is too low. Would be nice to be able to have sepia / grayscale while still being able to distinguish links.

exelente asi sabre cuando se aga tarde

Makes the screen flash with white flashes, really annoying...

Probably the best but makes firefox load pages about 2-3 seconds slower:/