You can export them from GIMP as a MNG (which is the animated form of PNG), which exports each layer as a separate animation frame, because of course it does, what a convenient way to animate things.

You can then feed the MNG to ImageMagick convert, targeting PDF which converts every frame back into a PDF page, because of course it does what a convenient way to make a flick book.

This probably would work with GIF animation too.

You're welcome. #2017yearoflinuxonthedesktop