I return! Another question, how did you make it so when you stamp a paper the stamp prefab doesn't bleed over the paper? Originally, I thought it was sprite masks, but that doesn't seem right since they would appear when hovering over a second paper.
We did use sprite masks! On UI layers you can have it so that sprite masks apply only to a specific range of sorting orders (eg z levels 1 through 3). We made it so that page objects use even-numbered z layers and any contents on the page (signatures, check marks, stamps) use the z layer directly above its page. That way if you have a letter with s.order 0 and another with s.order 2, the stamp on letter 0 has s.order 1, which is masked by letter 2.