PDFBox can do this but to have to build the CLI tool yourself from this example: https://github.com/apache/pdfbox/blob/5b00807463279f1002e24531aa0f07c12ee03b0d

PDFBox can do this but to have to build the CLI tool yourself from this example: https://github.com/apache/pdfbox/blob/5b00807463279f1002e24531aa0f07c12ee03b0d/examples/src/main/java/org/apache/pdfbox/examples/signature/CreateSignature.java https://github.com/apache/pdfbox/blob/5b00807463279f1002e245... Everything about PDF signatures is maddeningly complex.