Just type ATTACH at the command line.  For Files of type: select All image files and then navigate to your JPG.  It's just like bringing an xref drawing into your workspace.

Dave.

Just remember that images are raster-based files meaning they are resolution dependent.  As you scale them up you'll loose that nice crisp look.

Attaching images to CAD files uses the same process as xref-ing drawing files.  Image imports this way are called "underlays"  Bringing image files into a drawing is much better done this way than via copy/paste also.  You have more functionality.

Dave.

That's an interesting question... and one I never played with before.  But here's what I found out:

First, yes, you could change the image file without modifying the underlay in the drawing.  But you'd have to be careful because when you next open the file or reload the overlay it will update with the changes.  You'd need to bind it in the drawing if you wanted a particular version to remain static.

But I also discovered that having an image underlay in an open drawing prevents you from saving changes in a program like photoshop.  That's different behavior than changing a dwg xref.  There if you change the xref AutoCAD will give you a warning that it's changed.  This kind of message won't happen with an underlay.  But you can close the drawing and then modify the image.  But again, when you reload or reopen the drawing you'll get the updated image.  So be careful.  Changing filenames of images, if that's part of the workflow, is probably your solution.

Dave.