Copyright information can be contained both in the EXIF data and in the IPTC data. IPTC data are more comprehensive and I suggest to compile the relevant fields also in the IPTC data. IPTC fields are probably less likely to be stripped than EXIF fields. (EXIF fields serve mainly to contain information about the device, such as the scanner, while IPTC fields have the exact purpose to contain information about the image and the photographer).
IPTC fields exist in various flavours: for being a standard, it definitely it is not standardised. Even the label of the fields is not standardised. Anyway there are two fields, "Photographer" and "Copyright" which should be compiled always. You may also find fields "Photographer URL" and various other fields with contact information of the photographer. Depends on the IPTC implementation of your application and the IPTC "revision" the application is taking into consideration.

I would also embed a small visible watermark on the lower right corner of the scan. That will not detract from the image and will sign your work. Or you can make a frame around the image with the signature on the lower right corner.

Prints would be signed on the back with a pencil as customary.