The only person who can get away with forgery is a document expert who knows all the tricks.
Even then it is difficult, because it is so easy to make a mistake that another expert will find.
Incredibly stupid mistakes are made in forgeries, like the famed Howard Hughes will, the Hitler Diaries, etc.
The only hope for the non-expert forger is that the document will never be questioned in the first place, never subjected to expert analysis. Once the experts get it, the end is certain.