set a pdf file as NSButton's image

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i want to set a pdf file as a NSButton's image, and when i clicked the button,the button's color changed, just like the xcode's navigator editor. can some one tell me how to do this? thanks in advance

just refer these two answers
http://stackoverflow.com/questions/4107850/how-can-i-programatically-generate-a-thumbnail-of-a-pdf-with-the-iphone-sdk
http://stackoverflow.com/questions/5658993/creating-pdf-thumbnail-in-iphone