At least Manjaro Deepin can’t open PDFs out of the box. It would be nice if a PDF reader is included by default.
The best option seems to be Evince because:
When searching a document it lists all matches, instead of searching one by one. This is super useful.
Font dithering works when the screen is scaled. In Okular and qpdfview the hole interface is notably pixelated.
I can help out with that, if you wish.