Post date: Apr 17, 2015 4:14:16 PM
When you import a pdf in gimp it will load every page into separate layers.
You can edit every layer as you see fit.
After editing you should use the layer menu and reverse the order(Layer/Stack/Reverse Layer Order).
Then export it as a mng animation.
After that, you can use the "convert" program to convert it back to pdf
convert infile.mng outfile.pdf
Now you have a multi-page pdf file