选D have sth done表示某物被...sth与主语为被动关系,句中为一个宾语从句套一个定语从句,paper在句中作宾语,所以省去了that或which,还原为 I had the paper prepared,又加了个had done表示过去完成时, I had had the paper prepared,我之前准备好的纸。
D have sth done表示让人做某事,这里是当定语用,表示让人准备好的纸。
have sth done 有被动含义、
整理一下语序,I had had the paper prepared 前面一个had是过完 后面的是have sth done
是不是多打了一个had