I was looking for some free – like in free beer – alternatives to PDF Expert, the reader I’ve been using for years for its invert colours feature but can’t install anymore (both my licences are not recognised anymore). I found Negative.
This cool little app doesn’t seem to have any tool (no highlighter, no handwriting, no annotations, and so on). But it’s small, fast, free. And it does what it says:
Negative, free on the App Store.