I have set up a form and am going through the security options. I have unticked the 'print' box and the 'edit form' box and the 'delete' box but other users are still able to do all of them. Is there anything else I need to select to stop this occurring?

You will need to save the changes to the form, close the form and then reopen it.  You also need to ensure that you  have "Enabled" the security settings you have changed.  There is an Enable button in that security dialogue box that you need to click.