A Developer's Guide to Digitally Signing PDFs with C

使用 X509Certificate2 對象

為了實現最大程度的控制，您可以從憑證檔案建立 @@--CODE - 236--@@ 物件。 IronPDF 完全符合 X509Certificate2 標準，為數位簽章實作提供了強大且安全的方法。 建立憑證物件時，請確保將 X509KeyStorageFlags 設定為 Exportable，因為底層加密 API 要求這樣做。您可以在我們的程式碼庫中查看數位簽名的實際範例。

Install-Package IronPdf

using IronPdf;
using IronPdf.Signing;
using System.Security.Cryptography.X509Certificates;

// Create a new PDF from an HTML string for demonstration.
var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf("<h1>Signed Document</h1><p>This document has been digitally signed.</p>");

// Load the certificate from a .pfx file with its password.
// The X509KeyStorageFlags.Exportable flag is crucial for allowing the private key to be used in the signing process.
var cert = new X509Certificate2("IronSoftware.pfx", "123456", X509KeyStorageFlags.Exportable);

// Create a PdfSignature object using the loaded certificate.
var signature = new PdfSignature(cert);

// Apply the signature to the PDF document.
pdf.Sign(signature);

// Save the securely signed PDF document.
pdf.SaveAs("Signed.pdf");

using IronPdf;
using IronPdf.Signing;
using System.Security.Cryptography.X509Certificates;

// Create a new PDF from an HTML string for demonstration.
var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf("<h1>Signed Document</h1><p>This document has been digitally signed.</p>");

// Load the certificate from a .pfx file with its password.
// The X509KeyStorageFlags.Exportable flag is crucial for allowing the private key to be used in the signing process.
var cert = new X509Certificate2("IronSoftware.pfx", "123456", X509KeyStorageFlags.Exportable);

// Create a PdfSignature object using the loaded certificate.
var signature = new PdfSignature(cert);

// Apply the signature to the PDF document.
pdf.Sign(signature);

// Save the securely signed PDF document.
pdf.SaveAs("Signed.pdf");

上面的程式碼首先產生一個簡單的PDF檔案。 然後，它將 .pfx 憑證檔案載入到 X509Certificate2 物件中。 此物件代表數位身份，並傳遞給 PdfSignature 建構函數。 最後，pdf.Sign 方法在儲存文件之前將此簽章套用至文件。 For more information on the X509Certificate2 class, you can refer to the official Microsoft documentation.

為數位簽名添加詳細信息

數位簽章可以包含憑證以外的內容； 您可以嵌入豐富的元數據，以提供有關簽名的上下文資訊。 這包括簽署地點、原因、聯絡資訊以及來自可信任機構的安全時間戳。 您也可以設定和編輯元資料，以取得額外的文件屬性。

添加這些細節可以改進文件的審計跟踪，並為核實人員提供有價值的資訊。 IronPDF也支援使用現代 SHA256 和 SHA512 雜湊演算法的時間戳伺服器。

using IronPdf;
using IronPdf.Signing;
using IronSoftware.Drawing;
using System;

// Load an existing PDF document to be signed.
var pdf = PdfDocument.FromFile("invoice.pdf");

// Create a PdfSignature object directly from the certificate file and password.
var signature = new PdfSignature("IronSoftware.pfx", "123456");

// Add detailed metadata to the signature for a comprehensive audit trail.
// These properties enhance the signature's credibility and provide context
signature.SignatureDate = DateTime.Now;
signature.SigningContact = "legal@ironsoftware.com";
signature.SigningLocation = "Chicago, USA";
signature.SigningReason = "Contractual Agreement";

// Add a secure timestamp from a trusted Time Stamp Authority (TSA).
// This provides cryptographic proof of the signing time.
signature.TimeStampUrl = new Uri("[http://timestamp.digicert.com](http://timestamp.digicert.com)");
signature.TimestampHashAlgorithm = TimestampHashAlgorithms.SHA256;

// Apply a visual appearance to the signature. (More on this in the next section)
signature.SignatureImage = new PdfSignatureImage("assets/visual-signature.png", 0, new Rectangle(350, 750, 200, 100));

// Sign the PDF document with the configured signature object.
pdf.Sign(signature);

// Save the final, signed PDF document.
pdf.SaveAs("DetailedSignature.pdf");

using IronPdf;
using IronPdf.Signing;
using IronSoftware.Drawing;
using System;

// Load an existing PDF document to be signed.
var pdf = PdfDocument.FromFile("invoice.pdf");

// Create a PdfSignature object directly from the certificate file and password.
var signature = new PdfSignature("IronSoftware.pfx", "123456");

// Add detailed metadata to the signature for a comprehensive audit trail.
// These properties enhance the signature's credibility and provide context
signature.SignatureDate = DateTime.Now;
signature.SigningContact = "legal@ironsoftware.com";
signature.SigningLocation = "Chicago, USA";
signature.SigningReason = "Contractual Agreement";

// Add a secure timestamp from a trusted Time Stamp Authority (TSA).
// This provides cryptographic proof of the signing time.
signature.TimeStampUrl = new Uri("[http://timestamp.digicert.com](http://timestamp.digicert.com)");
signature.TimestampHashAlgorithm = TimestampHashAlgorithms.SHA256;

// Apply a visual appearance to the signature. (More on this in the next section)
signature.SignatureImage = new PdfSignatureImage("assets/visual-signature.png", 0, new Rectangle(350, 750, 200, 100));

// Sign the PDF document with the configured signature object.
pdf.Sign(signature);

// Save the final, signed PDF document.
pdf.SaveAs("DetailedSignature.pdf");

如果簽章憑證不在系統的受信任儲存區中，您可能會在某些 PDF 檢視器中看到警告圖示。 要獲得綠色對勾，必須將憑證新增至查看者的受信任身分。

儲存並簽署特定 PDF 版本

PDF 檔案可以儲存變更歷史記錄，就像版本控制系統一樣。 這稱為增量儲蓄。 當你簽署PDF文件時，該簽名僅適用於該文件的特定版本。 對於文件需要經過多個審批階段的工作流程來說，這一點至關重要。 請閱讀我們的詳細指南，以了解更多關於管理PDF修訂歷史記錄的資訊。

在以下範例中，我們載入一個 PDF 文件，進行編輯，然後簽署目前版本，同時只允許填寫表單作為未來的變更。 我們使用 SaveAsRevision 在儲存文件之前將目前狀態提交到文件的歷史記錄中。

using IronPdf.Signing;

// Load a PDF file with change tracking enabled.
// This enables incremental save functionality for revision management
var pdf = PdfDocument.FromFile("annual_census.pdf", ChangeTrackingModes.EnableChangeTracking);

// Placeholder for edits: You might add text, fill forms, or add annotations here.
// For example: pdf.Annotations.Add(new TextAnnotation(...));
// Or: pdf.Form["fieldName"].Value = "New Value";

// Sign the current state of the document using SignWithFile for convenience.
// We set permissions to allow further signatures and form filling.
pdf.SignWithFile(
    "assets/IronSignature.p12", 
    "password", 
    SignaturePermissions.AdditionalSignaturesAndFormFillingAllowed);

// Save the current state as a distinct revision within the PDF's history.
// This creates a snapshot that can be referenced later
PdfDocument pdfWithRevision = pdf.SaveAsRevision();

// Save the final PDF with its full revision history to a new file.
pdfWithRevision.SaveAs("annual_census_signed.pdf");

using IronPdf.Signing;

// Load a PDF file with change tracking enabled.
// This enables incremental save functionality for revision management
var pdf = PdfDocument.FromFile("annual_census.pdf", ChangeTrackingModes.EnableChangeTracking);

// Placeholder for edits: You might add text, fill forms, or add annotations here.
// For example: pdf.Annotations.Add(new TextAnnotation(...));
// Or: pdf.Form["fieldName"].Value = "New Value";

// Sign the current state of the document using SignWithFile for convenience.
// We set permissions to allow further signatures and form filling.
pdf.SignWithFile(
    "assets/IronSignature.p12", 
    "password", 
    SignaturePermissions.AdditionalSignaturesAndFormFillingAllowed);

// Save the current state as a distinct revision within the PDF's history.
// This creates a snapshot that can be referenced later
PdfDocument pdfWithRevision = pdf.SaveAsRevision();

// Save the final PDF with its full revision history to a new file.
pdfWithRevision.SaveAs("annual_census_signed.pdf");

理解增量保存是進階 PDF 工作流程的關鍵。 雖然簡單的檢視器可能只會顯示最新版本，但像 Adob​​e Acrobat 這樣的工具可以顯示完整的修訂歷史記錄，顯示誰簽署了哪個版本以及簽名之間做了哪些更改。 IronPDF讓您可以完全透過程式控制此流程。

對於管理複雜文件工作流程且需要高度安全性和合規性的企業而言，可能需要一個全面的解決方案。 Iron Software提供Iron Suite ，其中包括用於簽名和操作的IronPDF ，以及其他用於各種文件處理任務的庫，只需一次性付款即可獲得。

如何管理和驗證不同版本中的簽名？

PDF 文件可以在其各個版本中使用多個簽章。 IronPDF提供了有效管理此歷史記錄的工具。

-回滾到先前的版本：您可以使用 GetRevision 方法將文件還原到先前的狀態。 這將丟棄該版本之後所做的所有更改和簽名。
-驗證所有簽章：VerifySignatures 方法檢查文件所有版本中所有簽章的有效性。 只有當所有簽名都有效且沒有進行任何未經授權的更改時，才會返回 true。
-刪除簽名：RemoveSignatures 方法將從文件的每個版本中剝離所有數位簽名，創建一個乾淨的、未簽名的版​​本。

// Load a PDF with a complex signature history.
var pdf = PdfDocument.FromFile("multi_signed_report.pdf");

// Verify all signatures across all revisions.
// This ensures document integrity throughout its entire history
bool allSignaturesValid = pdf.VerifySignatures();
Console.WriteLine($"All signatures are valid: {allSignaturesValid}");

// Roll back to the first revision (index 0).
// Useful for reviewing the original document state
if (pdf.RevisionCount > 1)
{
    PdfDocument firstRevision = pdf.GetRevision(0);
    firstRevision.SaveAs("report_first_revision.pdf");
}

// Create a completely unsigned version of the document.
// This removes all digital signatures while preserving content
pdf.RemoveSignatures();
pdf.SaveAs("report_unsigned.pdf");

// Load a PDF with a complex signature history.
var pdf = PdfDocument.FromFile("multi_signed_report.pdf");

// Verify all signatures across all revisions.
// This ensures document integrity throughout its entire history
bool allSignaturesValid = pdf.VerifySignatures();
Console.WriteLine($"All signatures are valid: {allSignaturesValid}");

// Roll back to the first revision (index 0).
// Useful for reviewing the original document state
if (pdf.RevisionCount > 1)
{
    PdfDocument firstRevision = pdf.GetRevision(0);
    firstRevision.SaveAs("report_first_revision.pdf");
}

// Create a completely unsigned version of the document.
// This removes all digital signatures while preserving content
pdf.RemoveSignatures();
pdf.SaveAs("report_unsigned.pdf");

加蓋印章後的 PDF 結果是什麼樣子的？

程式碼運行後，簽名圖像會被印在文件上，從而產生一張帶有視覺簽名的發票。

最終的PDF檔案右下角蓋有手寫簽名印章。