Hi!
What I have done in JUDE to reduce my diagrams size is:
- Click in zoom out
- Click in Edit/Select All
- Click in Edit/Copy to clipboard
- Open MsPaint
- Click in Edit/Paste
- Save your image
You can zoom in or zoom out the diagram in Jude, copy to MsPaint and see the obtained results. Just try it!
I hope this could work for you. It worked to me. As a additional suggestion, save the image as PNG. Other hint: some better photo editor softwares can save PNG files using less KB. I used Paint Shop Pro, that is a good choice.