--- title: "Signature" canonical_url: "https://www.nutrient.io/api/csharp/signing/signature/" md_url: "https://www.nutrient.io/api/csharp/signing/signature.md" last_updated: "2026-10-08T08:55:57.713Z" description: "Provides functionality for signing PDF documents. Supports both digital signatures (with certificate) and electronic signatures (visual only)." --- Provides functionality for signing PDF documents. Supports both digital signatures (with certificate) and electronic signatures (visual only). The `Signature` class enables adding signatures to PDF documents: Digital signatures use PFX/P12 certificates to cryptographically sign the document.Electronic signatures add visual representation (image/text) without cryptographic signing. For PAdES-B compliance, use CAdES signature mode (the default). For PAdES-T compliance, configure a `TimestampConfiguration` in the signature options. ```csharp using Nutrient; ``` ## Construction ```csharp public Signature() ``` ## Methods ### AddDocumentTimestamp ```csharp public void AddDocumentTimestamp(Document document, string outputPath, TimestampConfiguration timestamp) ``` Appends a document timestamp to a document, protecting its current state and its validation material. **Parameters** | Name | Type | Description | | ------------ | ------------------------------------------------------------------------ | --------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to timestamp. | | `outputPath` | `string` | The path where the updated PDF will be saved. | | `timestamp` | [`TimestampConfiguration`](/api/csharp/signing/timestamp-configuration/) | The timestamp authority configuration. | ```csharp public void AddDocumentTimestamp(Document document, Stream output, TimestampConfiguration timestamp) ``` Appends a document timestamp to a document, writing the result to a stream. **Parameters** | Name | Type | Description | | ----------- | ------------------------------------------------------------------------ | -------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to timestamp. | | `output` | `Stream` | The output stream where the updated PDF will be written. | | `timestamp` | [`TimestampConfiguration`](/api/csharp/signing/timestamp-configuration/) | The timestamp authority configuration. | ### AddLtvInformation ```csharp public void AddLtvInformation(Document document, string outputPath) ``` Adds long-term validation material — certificates and revocation information — for all signed signatures of a document, upgrading it toward PAdES B-LT. **Parameters** | Name | Type | Description | | ------------ | ----------------------------------- | -------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The signed document to add validation material to. | | `outputPath` | `string` | The path where the updated PDF will be saved. | ```csharp public void AddLtvInformation(Document document, Stream output) ``` Adds long-term validation material for all signed signatures, writing the result to a stream. **Parameters** | Name | Type | Description | | ---------- | ----------------------------------- | -------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The signed document to add validation material to. | | `output` | `Stream` | The output stream where the updated PDF will be written. | ### FinishSignature ```csharp public void FinishSignature(Document preparedDocument, string outputPath, Byte[] signedData, DigitalSignatureOptions options) ``` Completes external signing (phase two) with a raw signature value produced by an external signer. **Parameters** | Name | Type | Description | | ------------------ | --------------------------------------------------------------------------- | ------------------------------------------------------------------------ | | `preparedDocument` | [`Document`](/api/csharp/document/) | The prepared document returned by `PrepareSignature`. | | `outputPath` | `string` | The path where the signed PDF will be saved. | | `signedData` | `Byte[]` | The raw signature value over the prepared bytes. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options with the same certificate used to prepare. | ```csharp public void FinishSignature(Document preparedDocument, Stream output, Byte[] signedData, DigitalSignatureOptions options) ``` Completes external signing (phase two) with a raw signature value, writing the result to a stream. **Parameters** | Name | Type | Description | | ------------------ | --------------------------------------------------------------------------- | ------------------------------------------------------------------------ | | `preparedDocument` | [`Document`](/api/csharp/document/) | The prepared document. | | `output` | `Stream` | The output stream where the signed PDF will be written. | | `signedData` | `Byte[]` | The raw signature value over the prepared bytes. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options with the same certificate used to prepare. | ### FinishSignatureWithCms ```csharp public void FinishSignatureWithCms(Document preparedDocument, string outputPath, Byte[] signatureContainer) ``` Completes external signing (phase two) with a complete signature container produced by an external signing service. **Parameters** | Name | Type | Description | | -------------------- | ----------------------------------- | -------------------------------------------------- | | `preparedDocument` | [`Document`](/api/csharp/document/) | The prepared document. | | `outputPath` | `string` | The path where the signed PDF will be saved. | | `signatureContainer` | `Byte[]` | The complete, DER-encoded CMS signature container. | ```csharp public void FinishSignatureWithCms(Document preparedDocument, Stream output, Byte[] signatureContainer) ``` Completes external signing (phase two) with a complete signature container, writing the result to a stream. **Parameters** | Name | Type | Description | | -------------------- | ----------------------------------- | ------------------------------------------------------- | | `preparedDocument` | [`Document`](/api/csharp/document/) | The prepared document. | | `output` | `Stream` | The output stream where the signed PDF will be written. | | `signatureContainer` | `Byte[]` | The complete, DER-encoded CMS signature container. | ### PrepareSignature ```csharp public Byte[] PrepareSignature(Document document, string outputPath, DigitalSignatureOptions options) ``` Starts external signing (phase one): prepares the document with a signature placeholder and returns the exact bytes an external signer must sign. **Parameters** | Name | Type | Description | | ------------ | --------------------------------------------------------------------------- | ----------------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to prepare for signing. | | `outputPath` | `string` | The path where the prepared PDF will be saved. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options, including the signing certificate. | **Returns:** `Byte[]` - The bytes to be signed by the external signer. ```csharp public Byte[] PrepareSignature(Document document, Stream output, DigitalSignatureOptions options) ``` Starts external signing (phase one), writing the prepared PDF to a stream and returning the bytes an external signer must sign. **Parameters** | Name | Type | Description | | ---------- | --------------------------------------------------------------------------- | ----------------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to prepare for signing. | | `output` | `Stream` | The output stream where the prepared PDF will be written. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options, including the signing certificate. | **Returns:** `Byte[]` - The bytes to be signed by the external signer. ### Sign ```csharp public void Sign(Document document, string outputPath, DigitalSignatureOptions options) ``` Applies an invisible digital signature to a document. **Parameters** | Name | Type | Description | | ------------ | --------------------------------------------------------------------------- | ----------------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to sign. | | `outputPath` | `string` | The path where the signed PDF will be saved. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options including certificate and metadata. | ```csharp public void Sign(Document document, Stream output, DigitalSignatureOptions options) ``` Applies an invisible digital signature to a document, writing the result to a stream. **Parameters** | Name | Type | Description | | ---------- | --------------------------------------------------------------------------- | ----------------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to sign. | | `output` | `Stream` | The output stream where the signed PDF will be written. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options including certificate and metadata. | ### SignField ```csharp public void SignField(Document document, string outputPath, string fieldName, DigitalSignatureOptions? options, SignatureAppearance? appearance) ``` Applies a signature to a document using an existing signature field. Supports both digital signatures (with certificate) and electronic signatures (visual only). **Parameters** | Name | Type | Description | | ------------ | --------------------------------------------------------------------------- | ----------------------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to sign. | | `outputPath` | `string` | The path where the signed PDF will be saved. | | `fieldName` | `string` | The name of the existing signature form field to use for the signature. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options. Can be null for electronic signatures. | | `appearance` | [`SignatureAppearance`](/api/csharp/signing/signature-appearance/) | The visual appearance of the signature. | ```csharp public void SignField(Document document, Stream output, string fieldName, DigitalSignatureOptions? options, SignatureAppearance? appearance) ``` Applies a signature to a document using an existing signature field, writing the result to a stream. Supports both digital signatures (with certificate) and electronic signatures (visual only). **Parameters** | Name | Type | Description | | ------------ | --------------------------------------------------------------------------- | ----------------------------------------------------------------------- | | `document` | [`Document`](/api/csharp/document/) | The document to sign. | | `output` | `Stream` | The output stream where the signed PDF will be written. | | `fieldName` | `string` | The name of the existing signature form field to use for the signature. | | `options` | [`DigitalSignatureOptions`](/api/csharp/signing/digital-signature-options/) | The digital signature options. Can be null for electronic signatures. | | `appearance` | [`SignatureAppearance`](/api/csharp/signing/signature-appearance/) | The visual appearance of the signature. | ## Resource management ```csharp public void Dispose() ``` `Signature` implements `IDisposable` and owns native resources. Always call `Dispose()` or use a C# `using` declaration: it is not released automatically. --- ## Related pages - [Signing](/api/csharp/signing.md) - [Digital Signature Options](/api/csharp/signing/digital-signature-options.md) - [Pkcs11 Options](/api/csharp/signing/pkcs11-options.md) - [Signature Appearance](/api/csharp/signing/signature-appearance.md) - [Timestamp Configuration](/api/csharp/signing/timestamp-configuration.md)