This Chapter is dedicated to present digital watermarking technology and mainly to propose how it can be used to protect digital documents (copyright protection). In the field of Cultural Heritage (CH), the protection of images is a crucial issue, stated the importance of their diffusion, both with dissemination aims and in order to attract visitors to real museums. Digital marking techniques are a key application for the protection of Cultural Heritage digital images.
In the following, digital marking techniques are presented, with particular attention to the \u201cperceptual\u201d invisibility of the mark (in order to not deteriorate the image itself) and \u201crobustness\u201d (the strength of the mark, that is its resistance to be removed). Examples concerning art-works of the Polo Museale Fiorentino are shown
