Nutrient .NET SDK
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PDF SIGNING IN C#
using GdPicturePDF gdPicturePDF = new GdPicturePDF();gdPicturePDF.LoadFromFile(@"C:\temp\source.pdf");
// Set the certificate from a PKCS#12 file.gdPicturePDF.SetSignatureCertificateFromP12( @"C:\temp\certificate.pfx", "password");
// Add signer information.gdPicturePDF.SetSignatureInfo( "John Smith", "Approval", "Vienna", "john@example.com");
// Position the signature on the last page.gdPicturePDF.SetMeasurementUnit( PdfMeasurementUnit.PdfMeasurementUnitCentimeter);gdPicturePDF.SelectPage(gdPicturePDF.GetPageCount());gdPicturePDF.SetSignaturePos(10, 10, 5, 2);
// Apply and save.gdPicturePDF.ApplySignature(@"C:\temp\output.pdf", PdfSignatureMode.PdfSignatureModeAdobePPKMS, false);using GdPicturePDF gdPicturePDF = new GdPicturePDF();gdPicturePDF.LoadFromFile(@"C:\temp\source.pdf");
// Set the certificate from a PKCS#12 file.gdPicturePDF.SetSignatureCertificateFromP12( @"C:\temp\certificate.pfx", "password");
// Add certificate information.gdPicturePDF.SetSignatureInfo( "John Smith", "Certified", "Vienna", "john@example.com");
// Certify and save.gdPicturePDF.ApplySignature(@"C:\temp\output.pdf", PdfSignatureMode.PdfSignatureModeAdobePPKMS, false);using GdPicturePDF gdPicturePDF = new GdPicturePDF();gdPicturePDF.LoadFromFile(@"C:\temp\source.pdf");gdPicturePDF.SelectPage(1);
// Set coordinate system and units.gdPicturePDF.SetMeasurementUnit( PdfMeasurementUnit.PdfMeasurementUnitCentimeter);gdPicturePDF.SetOrigin( PdfOrigin.PdfOriginBottomRight);
// Add a signature field.int fieldId = gdPicturePDF.AddSignatureFormField( 2, 5, 5, 2, "Signature1");
// Configure the field appearance.string font = gdPicturePDF.AddTrueTypeFont( "Freestyle Script", false, false, false);gdPicturePDF.SetFormFieldFontResName(fieldId, font);gdPicturePDF.SetFormFieldFontSize(fieldId, 48);
gdPicturePDF.SaveToFile(@"C:\temp\output.pdf");USE CASES
Sign contracts, agreements, and NDAs programmatically. Load a PDF, apply a PKCS#12 certificate, and save the signed output — no manual signing step required.
Certify PDFs to prove authenticity and detect any post-signing modification. Any change to a certified document is flagged when a PDF is opened.
Add signature fields to PDFs before distributing them. Recipients fill the prepared fields with their own digital signatures.
Customize how signatures look on the page — add signer name text, a scanned handwritten signature image, or both inside the signature bounding box.
Apply a PKCS#12 certificate to a PDF. Position the signature on any page, add signer metadata, and save the signed document.
Add a certificate to prove document authenticity. Any modification after certification is detected and flagged.
Add signature form fields, fill existing ones, and read their properties — ID, name, font, size, and color.
Control how signatures look on the page. Add text, an image (such as a scanned handwritten signature), or both.
ADVANCED CAPABILITIES
The SDK handles more than applying a single signature. Work with multiple signatures, load certificates from different sources, control signature positioning down to the pixel, and integrate signing into batch processing workflows.
Apply more than one digital signature to a document. Each signature is independent and can use a different certificate.
Load certificates from PKCS#12 files on disk or from stream objects — compatible with certificates stored in databases, key vaults, or memory.
No GUI dependencies — sign PDFs in background jobs, Windows services, or API handlers. Process stacks of documents in a loop.
After signing, any modification to the document is noted. Certified documents flag changes when opened in any compliant PDF reader.
Load the PDF, set the certificate from a PKCS#12 file, optionally add signer information (name, reason, location), position the signature on a page, and call the apply method to save the signed document. See the digital signature guide for a complete working example.
Signing applies a digital signature that authenticates the signer’s identity. Certifying goes further — it also locks the document so any post-certification change is detected and flagged. Both use PKCS#12 certificates. See the certify guide.
Load the PDF, set the coordinate origin and measurement unit, and call the method to add a signature form field with position, dimensions, and a field name. Recipients can then fill the prepared field with their own digital signature. See the add signature field guide.
Yes. You can add text (with custom font, size, color, and alignment), a JPEG image (such as a scanned handwritten signature), or both inside the signature bounding box. If both are used, the image is placed to the right of the text. See the signature guide for text and image examples.
The SDK accepts certificates from PKCS#12 files (.pfx or .p12) and from stream objects. This means you can load certificates from disk, from a database, from a key vault, or from any source that provides a stream.
Yes. If you skip setting the signature position and dimensions, the signature is applied as an invisible signature. The document is cryptographically signed, but no visual element appears on any page. Invisible signatures are useful for automated workflows where visual appearance isn’t needed.
Yes. The SDK supports documents with multiple signatures. Each signature is independent and can use a different certificate, signer information, and appearance. This is common in approval workflows where several parties need to sign the same document.
Yes. The SDK is a standard .NET library with no GUI dependencies. Loop through your PDF files, apply signatures, and save the results in a console application, Windows service, background job, or API handler.
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