More like a sheet of paper held up to the light. Some light gets through, and if you have thicker paper it will allow less light through, but it doesn't noticeably damage the paper.
Depends how long you leave the paper exposed to light. if you have a sheet of paper half exposed and half shielded for a year of sunlight the effect is marked.
The equivalent in lead would probably manifest in some way, perhaps a visible patina on the surface? or, as a differential in decay products. you could call that 'damage' if you wanted to.
The equivalent in lead would probably manifest in some way, perhaps a visible patina on the surface? or, as a differential in decay products. you could call that 'damage' if you wanted to.