Also I remember seeing screenshots where PDFs looked transparent or matched the terminal colors. Is that actually a feature of some of these viewers ?
Zathura lets you recolour and theme pdfs, yes. See zathurarc(5). You can set alpha using "rgba(r, g, b, a)" when setting a colour, e.g. set to 0.8 for 0.8 opacity.








Outdated how? I use it for my daily driver and it works fine for me. It’s a fairly simple program and the 0.3.x river protocol is fairly stable so I would doubt it’s become outdated, but if it is, you should be able to patch it yourself given the simplicity of the program.