iText 9 Signing Improvements

In iText 9, we’ve made several important updates to improve the creation and handling of signature form fields, ensuring better PDF/UA compliance and a smoother developer experience. Previously, when signing a document that did not have any available signature fields, causing a new one to be created, the AlternativeDescription set in the GetAccessibilityProperties of the appearance of the new signature field was not considered.

This omission led to a missing description entry (known as the Tooltip or TU entry), which is crucial for accessibility. Without it, the document fails PDF/UA validation, making it non-compliant. Modifying the form field properties requires developers to override methods, which can quickly become complicated and unintuitive.

Additionally, past versions did not alert users when a font was not set for the SignatureAppearance when working with PDF/UA documents. Previously, this would result in a PropertyError rather than a more informative PDF/A or PDF/UA compliance exception.

In our latest release, these challenges have been addressed, and creating a signature form field now correctly incorporates the AlternativeDescription, helping ensure your documents meet PDF/UA standards more easily.

We’ve also enhanced the way SignatureAppearance handles font settings, offering clearer warnings to prevent confusion and reduce errors while creating accessible documents.

Code

To sign PDF/UA documents, we’ll need to inherit from the PdfSigner (Java/.NET) class to create a PdfUaSigner that is instantiated with the PdfUaDocument (Java/.NET) object. Below you can find a simple example implementation for this.

Once the PdfSigner is properly instantiated with a PdfUADocument, we can follow the normal signing workflow as described in our Digital Signing with iText series on the Knowledge Base. The PdfUaDocument will ensure PDF/UA is being adhered to during document generation.

Java

JAVA

        static class PdfUaSigner extends PdfSigner {

        public PdfUaSigner(PdfReader reader, OutputStream outputStream, StampingProperties properties) throws IOException {
            super(reader, outputStream, properties);
        }

        public PdfUaSigner(PdfReader reader, OutputStream outputStream, String path, StampingProperties stampingProperties, SignerProperties signerProperties) throws IOException {
            super(reader, outputStream, path, stampingProperties, signerProperties);
        }

        public PdfUaSigner(PdfReader reader, OutputStream outputStream, String path, StampingProperties properties) throws IOException {
            super(reader, outputStream, path, properties);
        }

        @Override
        protected PdfDocument initDocument(PdfReader reader, PdfWriter writer, StampingProperties properties) {
            return new PdfUADocument(reader, writer, new PdfUAConfig(PdfUAConformanceLevel.PDFUA_1, "Title", "en-US"));
        }
    }

C#

         internal class PdfUaSigner : PdfSigner {
            public PdfUaSigner(PdfReader reader, Stream outputStream, StampingProperties properties)
                : base(reader, outputStream, properties) {
            }

            public PdfUaSigner(PdfReader reader, Stream outputStream, String path, StampingProperties stampingProperties
                , SignerProperties signerProperties)
                : base(reader, outputStream, path, stampingProperties, signerProperties) {
            }

            public PdfUaSigner(PdfReader reader, Stream outputStream, String path, StampingProperties properties)
                : base(reader, outputStream, path, properties) {
            }

            protected internal override PdfDocument InitDocument(PdfReader reader, PdfWriter writer, StampingProperties
                 properties) {
                return new PdfUADocument(reader, writer, new PdfUAConfig(PdfUAConformance.PDF_UA_1, "Title", "en-US"));
            }
        }