This page is interesting. It shows how to supress the In[]/Out[] commands only in a print-out of the document:

http://mathematica.stackexchange.com/questions/1135/removing-in-out-labels-before-printing

M.

One approach is to create a new stylesheet...  or to edit the private stylesheet for the notebook.  

For an example of the latter, choose the Format>Edit Stylesheet menu item.
Then in the "Chooose a Style" dropdown menu choose "Output".  
Then select the cell bracket of the Output  that has been placed in the private stylesheet  and choose the Cell>ShowExpression menu item. 
In the displayed cell expression change it to

Then unselect the  Cell>ShowExpression menu item and close the private stylesheet.  

The result is that your Output cells will no longer have the Out cell lables.