how to create an UIImage by pdf file in Xcode : [use the pdf as icon][1]


  [1]: http://i.stack.imgur.com/N3OVK.png

when i want to use the pdf icon in project,i do like this 

    [UIImage imageNamed:@"icon_file_open"];

but is that ok? [UIImage imageNamed:] will always retain the image in memory,is there any other way that i can create the image by pdf?