Well as someone with an education in nanomaterials, I'm going to have to agree with you that using a particular ink that reacts to UV in a specific way sounds like a fantastic idea for a "watermark" that doesn't appear to be a watermark unless you're in on the plan. You could even get them printed without anyone involved in the actual design or printing knowing they were watermarked, by controlling their ink supply.

Well as someone with an education in nanomaterials, I'm going to have to agree with you that using a particular ink that reacts to UV in a specific way sounds like a fantastic idea for a "watermark" that doesn't appear to be a watermark unless you're in on the plan. You could even get them printed without anyone involved in the actual design or printing even knowing they were watermarked, by controlling their ink supply.