Scan it into a graphic format file such as a JPEG and insert that into a container field. You can now put this container field anywhere you need the signature printed. (Please set up good security on your system so that the unauthorized can't get into mischief with your signature...)
I scanned the image as a jpeg, created a signature (container field), put the field on the layout, pasted the jpeg into the field as a picture in the layout mode, and it is still a large 8X10 image that distorts the image when I try to resize it.
What am I doing wrong?
Most scanners can crop the scanned image at the time you scan it. That would keep down the size of the image file you are inserting. You can also open the image file with a image editor such as Windows Paint and use it to crop your image.
You can also use data formatting options for the field to set it to crop or scale the scanned image, but this leaves the entire image inserted in the container--it just controlls how it is displayed.