You can instead use a drawing canvas with fixed resolution and paste the images on the canvas. Say, set canvas resolution to 500x500, resize it to the image size, then paste, then use "DrawingCanvas Save Image" action. The resulting PNG should be 500x500 px.
Or, if there are too many objects to paste - make a snapshot, load it into a sprite, paste the sprite onto the canvas.
It will be several objects... think of a character generator, that allows you to change weapons, armor, hair... and all the values for strength etc.
This should then be printed on A4 which makes the resolution necessary.
The second option sounds intriguing but wouldn´t it just take the "low res" screenshot then and scale it up to the bigger resolution, making everything blurry?
Feels like there must be some sort of code snippet or something for it, but I´m more of a designer than a coder. :-P