A Dark Mode PDF Reader Competing with Adobe

I really could use a pdf reader that smartly cleans up scanned pdf's with gray backgrounds and not so sharp type. And images.

I sometimes use the "export" in Apple's Preview.app with the Quartz filters to darken or lighten. "Black" filter does a decent job of thresholding, but sometimes needs a prior lightening or darkening, since the Quartz filters are not adjustable.

And thresholding is mean to images. This should be well within the capability of non-AI software. If such exists, I may have ignored it due to sticker shock, "cloud only" or subscription fees. (Names withheld to protect the guilty. )

Open to suggestions, or consider this a suggestion.