Here is a Friday teaser for you - what is the difference between PR and Propaganda ? Current Governments spend a fortune on "spin" to influence the thinking of the electorate.
Joseph Goebbels was the original master of spin for the Nazi party and created the principles of propaganda. Item 7 on his list is as follows
7. Credibility alone must determine whether propaganda output should be true or false.
So if it is believable the truth is irrelevant - weapons of mass destruction spring to mind as well as the idea that the Middle East is crying out for our intervention.
I suppose the difference might be that to hire a propaganda agency would make a client look bad - PR seems more friendly.