When using the iPad, I employ Vectornator (this app is free) to import images, draw in the cuts as Bezier curves (aka splines) and scale them to the size I’d like them on the metal. It could also draw spirals for the use as backbones easily. Try a decay of 70%, it fits a Golden spiral.
There are many apps and downloadable software that will help you manipulate images. If you are simply looking to resize, you can run a Google search for free image resize. There are a few websites that will allow you to resize by uploading the image.
my fave way is to draw oversize. then scan the dwg, and then fiddle with it in corel. i don't use any software to create scroll. the resize in corel allows for very good transfers of any size i want. i recently began creating what i call master transfer patterns. i cut the different sizes onto an alluminum bar. then do the wax/clear tape trick. a time saver.