Cross a bit of what are unique in your document. Some things that are difficult to rebuild using Photoshop. Part of address. Part of the holoface. Part of your face. If you cross over just the top common like "Kad Pengenalan Malaysia", that they can simply superimpose with image of their own "Kad Pengenalan Malaysia".

It won't deter anyone determined, but it will make it arduous for petty opportunists.