Display Signature Validation like Adobe

[avrapps]

Apache PDFBox references this specification in its visible-signature implementation:

https://github.com/apache/pdfbox/blob/trunk/examples/src/main/java/org/apache/pdfbox/examples/signature/CreateVisibleSignature2.java

Historical Adobe signature appearances use structures/layers such as:

n0
n1
n2
n3
n4

The historical implementation is useful as a reference for understanding signature appearance composition.