1. Design the report that you wish to make a label invisible if the data associated with that label is empty
2. Click on the label you wish to hide.   For this example we will be using sales document number.
3. Click on the little arrow in the upper right corner of the control
4. Click on the gear icon
5. Scroll down to the visible setting and right click and click Expression.
6. Make the expression Iif(Len([SalesDocumentNumber])<1, false, true)
   1. If the field is something other than sales document number, find that field in the Fields list shown in the list below the expression editor and double click to add it to the expression)
7. When you print this report if the Sales Document Number is empty the label will hide as well!