I am using Sketch 3, and I suspect this feature is somewhere in the program, but I'm stuck.
My issue is, I'm unable to export all artboards across all the Pages in my .sketch document.
I have 2 Pages in my .sketch file: "Branding Elements" Page "Sign Up Screen" Page
Each page has multiple artboards that I want to export as .pngs, but for some reason I am only able to export the artboards that appear in the "Branding Elements" Page, and not the "Sign Up Screen" Page. The Sign Up artboards don't even show up in the little preview popup window.
Is this a bug, or user error (I am new to Sketch), or a feature that doesn't exist?
For a single page you can export all artboards at once like this:
Edit > Select all art boards
Layer > Make exportable
Now you can export art boards.