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Description
Using PDFBox v2.0 snapshot I tried to sign PDF/A document with invisible signature. I noticed that invisible signature annotation dictionary, when signature has been created with this method PDDocument#addSignature(:PDSignature, :SignatureInterface), is created with F key’s NoView flag bit set to 1 in Widget annotation dictionary (see: PDDocument.java#247):
// set visibility flags if (options.getVisualSignature() == null) { signatureField.getWidgets().get(0).setNoView(true); }
The use of this flag is redundant for making signature field invisible. As ISO 32000 states:
Signature fields that are not intended to be visible shall have an annotation rectangle that has zero height and width. Conforming readers shall treat such signatures as not visible.
Besides, the use of this flag violates PDF/A-1 (and PDF/A-2) requirements for Annotation dictionary F key:
The F key’s Print flag bit shall be set to 1 and its Hidden, Invisible and NoView flag bits shall be set to 0.