There are many lossless transformations that can be done on JPEGs:
- Rotate by 90 or 180 degrees in either direction
- Flip horizontally or vertically
- Transpose along either diagonal axis
- Modify only a small area of an image, and save the JPEG, while recompressing only that small part of the image.
Does Lightroom 5 support any of these? I can use another app, but I'd rather use Lightroom, so that I'll have the entire history of the edits and can undo or tweak them months or years later.