Image width as percentage of page width?

I’ve written a small user guide which I have publish as a Kindle book. This was composed using standard Scrivener settings (this is on version 1.9).

The book contains a few illustrations. The work well in the Kindle edition.

I’m trying to take the same file and publish as a paperback on KDP, and I’m using a 6x9 inch page dimension. I’ve printed out a PDF with those dimensions in the compile format, and I’ve got it to work fairly well, except for one thing - the images are now taking up more than the width of the page, so the right side of the image is being cut off.

Is there some way to import an image so that it’s width is specified as a percentage of the page width, so that it will shrink of expand to look as expected in any page size? Or is there any other technique to solve this problem?

Thanks for your help.