I've run into this with screen grabs from documentaries that were featured in some books I was designing. There were three books, with about 30-50 of these per book, and they were all square-pixel TIFs from non-square video frames, so I built the solution into an Action to save me the tedium of doing every one by hand. You should do the same if you're going to be running into this situation regularly.
When you create your DVD menu jpegs, you essentially get to the same starting point I had, so here's how you handle. The video frame is 960x720, but its correct aspect ratio should be 16:9, 1280x720. This approach, however, will work for any dimensions provided you know the correct output size.
Starting point is the original image:
Resize by checking "resample" and unchecking the aspect ratio lock:
Now you can drop the image into an InDesign layout, assemble into a PDF with the Bridge Output module or directly from within Acrobat, etc.