Some things in advance:

Every class you create for one diagram is known in each other diagram of the same
jude file. Actually they appear below the diagrams in your jude files structure.
From there you can drag and drop them to every other diagram.


How to hide operations and attributes in class diagram:

Mark every class, right click and turn "operation compartment visibility" 
and "attribute compartment visibility" off.


How to export single class diagram as image:

Select the class diagram, select the part you want to export as image 
(or nothing if the whole diagram should be exported) and choose 
"Tool->Export image->save diagram as png" from the menu.


How to export multiple class diagrams in the same jude file:

Choose "Tool->export image->save multiple diagrams as png" from the menu.
Mark the diagrams you want to export in the upcoming dialogue.
After clicking "ok" choose the folder where to save the images. The images 
will be saved as:

<your chosen folder>/<name of the jude file>/<diagram name>.png

