I was given a .pcb file and I'd like to view it to confirm it's a valid file and at least minimally what I was expecting.
ExpressPCB .pcb files are a proprietary format. I use MacOS so a native app isn't available and using Wine (the "free" version isn't actually free, in the end) or virtual machine aren't an option for this one file. It won't open nor import in KiCAD, Eagle nor LibrePCB. I tried a few graphic editors but none would open it.
There used to be an app called Copper Connection that would convert .pcb files but Express PCB bought this company a few years ago.
I'd even be happy with a .pdf file.