Applying Digital Signatures in IronPDF

Curtis Chau

Updated: July 21, 2026

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  # Applying Digital Signatures in IronPDF A digital signature is a cryptographic method that can be added to existing PDF documents using the IronPDF library. This includes adding [single](/how-to/signing/) and [multiple signatures with incremental savings](/how-to/revision-history/#save-and-sign-a-pdf-revision-iteration) signatures. ## Supported digital signature certificate IronPDF supports digital signature certificates in the `.pfx` format for Windows and `.p12` format for MacOS. These are compliant with the `X509Certificate2` standard. You can verify the format of your existing digital signature certificate by checking its file extension. If you do not have a certificate in the required format, refer to this [documentation](https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography.x509certificates.x509certificate2.-ctor?view=net-8.0) to create a new `X509Certificate2` standard certificate. The resulting certificate can then be used and applied to a PDF document via IronPDF. [[i:(IronPDF only supports `X509KeyStorageFlags.Exportable`. Some certificates have `KeyStorageFlags` set to Exportable by default. Attempting to use different `KeyStorageFlags` will result in an exception being thrown.)]] ## Signature with image An image can be added to the PDF document to visually indicate that the document has been digitally signed. This can be achieved using IronPDF with the following code snippet: ```csharp // Create a PdfSignature object by specifying the certificate file (.pfx) and its password var sig = new PdfSignature("IronSoftware.pfx", "123456"); // Set the signature image which includes the image path, page number, and its position in the document sig.SignatureImage = new PdfSignatureImage("IronSoftware.png", 0, new Rectangle(0, 600, 100, 100)); ``` Ensure that the image file property is set to `"CopyToOutputDirectory=always"` in the project so that the image can be found and rendered in the PDF document once the signature has been applied. To learn more about applying digital signatures via IronPDF, check out [Digitally Sign a PDF Document](/how-to/signing/). For engineering support, please see [How to Make an Engineering Support Request for IronPDF](/troubleshooting/engineering-request-pdf/).

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A digital signature is a cryptographic method that can be added to existing PDF documents using the IronPDF library. This includes adding single and multiple signatures with incremental savings signatures.

Supported digital signature certificate

IronPDF supports digital signature certificates in the .pfx format for Windows and .p12 format for MacOS. These are compliant with the X509Certificate2 standard. You can verify the format of your existing digital signature certificate by checking its file extension.

If you do not have a certificate in the required format, refer to this documentation to create a new X509Certificate2 standard certificate. The resulting certificate can then be used and applied to a PDF document via IronPDF.

Signature with image

An image can be added to the PDF document to visually indicate that the document has been digitally signed. This can be achieved using IronPDF with the following code snippet:

// Create a PdfSignature object by specifying the certificate file (.pfx) and its password
var sig = new PdfSignature("IronSoftware.pfx", "123456");

// Set the signature image which includes the image path, page number, and its position in the document
sig.SignatureImage = new PdfSignatureImage("IronSoftware.png", 0, new Rectangle(0, 600, 100, 100));

// Create a PdfSignature object by specifying the certificate file (.pfx) and its password
var sig = new PdfSignature("IronSoftware.pfx", "123456");

// Set the signature image which includes the image path, page number, and its position in the document
sig.SignatureImage = new PdfSignatureImage("IronSoftware.png", 0, new Rectangle(0, 600, 100, 100));

' Create a PdfSignature object by specifying the certificate file (.pfx) and its password
Dim sig = New PdfSignature("IronSoftware.pfx", "123456")

' Set the signature image which includes the image path, page number, and its position in the document
sig.SignatureImage = New PdfSignatureImage("IronSoftware.png", 0, New Rectangle(0, 600, 100, 100))

' Create a PdfSignature object by specifying the certificate file (.pfx) and its password
Dim sig = New PdfSignature("IronSoftware.pfx", "123456")

' Set the signature image which includes the image path, page number, and its position in the document
sig.SignatureImage = New PdfSignatureImage("IronSoftware.png", 0, New Rectangle(0, 600, 100, 100))

Ensure that the image file property is set to "CopyToOutputDirectory=always" in the project so that the image can be found and rendered in the PDF document once the signature has been applied.

To learn more about applying digital signatures via IronPDF, check out Digitally Sign a PDF Document.

For engineering support, please see How to Make an Engineering Support Request for IronPDF.

Curtis Chau

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Technical Writer

Curtis Chau holds a Bachelor’s degree in Computer Science (Carleton University) and specializes in front-end development with expertise in Node.js, TypeScript, JavaScript, and React. Passionate about crafting intuitive and aesthetically pleasing user interfaces, Curtis enjoys working with modern frameworks and creating well-structured, visually appealing manuals.

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