You can export an image from Sketch to your iPad directly. The resulting raster image can be sent to just about anything that will accept a raster image.
The .sket paths are less likely to be supported, but that's probably not a surprise for CS software that is 10 years old.
The iPad is only 2½ years old.
I suspect you posted in the wrong forum, this is the Sketch, not the InDesign forum.
Both are ancient versions. The CS3 user has to export as INX and you open it and save it as INDD, but await changes in your document.