将 PDF 转换为 PDF/A 格式

Aspose.PDF for .NET 允许您将 PDF 文件转换为 PDF/A 合规的 PDF 文件。在此之前，必须对文件进行验证。本文将解释如何进行验证。

• 将 PDF 转换为 PDF/A-1b
• 将 PDF 转换为 PDF/A-3b
• 将 PDF 转换为 PDF/A-4

我们遵循 Adobe Preflight 和 veraPDF 来验证 PDF/A 的符合性。市场上的所有工具都有自己对 PDF/A 符合性的“表示”。请查看本文关于 PDF/A 验证工具的参考。我们选择 Adobe 产品来验证 Aspose.PDF 生成 PDF 文件的方式，因为 Adobe 是与 PDF 相关的一切的中心。

使用 Document 类的 Convert 方法转换文件。在将 PDF 转换为符合 PDF/A 的文件之前，使用 Validate 方法验证 PDF。验证结果存储在 XML 文件中，然后该结果也传递给 Convert 方法。您还可以使用 ConvertErrorAction 枚举指定无法转换的元素的操作。

尝试在线将 PDF 转换为 PDF/A

Aspose.PDF for .NET 为您提供在线免费应用程序 “PDF to PDF/A-1A”，您可以尝试探索其功能和工作质量。

以下代码片段也适用于 Aspose.PDF.Drawing 库。

支持的标准

我们支持以下标准：PDF/A-1b、PDF/A-1a、PDF/A-2b、PDF/A-2u、PDF/A-2a、PDF/A-3b、PDF/A-3u、PDF/A-3a、PDF/A-4、PDF/A-4e、PDF/A-4f。

将 PDF 文件转换为 PDF/A-1b

将 PDF 转换为 PDF/A-1b

以下代码片段演示如何将 PDF 文件转换为 PDF/A-1b 合规的 PDF。

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfToPdfA()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();
    
    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf"))
    {
        // Convert to PDF/A compliant document
        // During conversion process, the validation is also performed
        document.Convert(dataDir + "PDFA1bConversionLog.xml", Aspose.Pdf.PdfFormat.PDF_A_1B, Aspose.Pdf.ConvertErrorAction.Delete);
        
        // Save PDF document
        document.Save(dataDir + "PDFToPDFA_out.pdf");
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfToPdfA()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();
    
    // Open PDF document
    using var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf");

    // Convert to PDF/A compliant document
    // During conversion process, the validation is also performed
    document.Convert(dataDir + "PDFA1bConversionLog.xml", Aspose.Pdf.PdfFormat.PDF_A_1B, Aspose.Pdf.ConvertErrorAction.Delete);
    
    // Save PDF document
    document.Save(dataDir + "PDFToPDFA_out.pdf");
}

要仅执行验证，请使用以下代码行：

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ValidatePdfAStandard()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();
    
    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "ValidatePDFAStandard.pdf"))
    {
        // Validate PDF for PDF/A-1a
        document.Validate(dataDir + "ValidationResultA1b.xml", Aspose.Pdf.PdfFormat.PDF_A_1B);
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ValidatePdfAStandard()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();

    // Open PDF document
    using var document = new Aspose.Pdf.Document(dataDir + "ValidatePDFAStandard.pdf");

    // Validate PDF for PDF/A-1a
    document.Validate(dataDir + "ValidationResultA1b.xml", Aspose.Pdf.PdfFormat.PDF_A_1B);
}

将 PDF 文件转换为 PDF/A-3b

将 PDF 转换为 PDF/A-3b

Aspose.PDF for .NET 还支持将 PDF 文件转换为 PDF/A-3b 格式的功能。

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfToPdfA3b()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();
    
    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf"))
    {
        // Convert to PDF/A compliant document, log file is omitted
        document.Convert(Stream.Null, Aspose.Pdf.PdfFormat.PDF_A_3B, Aspose.Pdf.ConvertErrorAction.Delete);
        
        // Save PDF document
        document.Save(dataDir + "PDFToPDFA3b_out.pdf");
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfToPdfA3b()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();

    // Open PDF document
    using var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf");

    // Convert to PDF/A compliant document, log file is omitted
    document.Convert(Stream.Null, Aspose.Pdf.PdfFormat.PDF_A_3B, Aspose.Pdf.ConvertErrorAction.Delete);

    // Save PDF document
    document.Save(dataDir + "PDFToPDFA3b_out.pdf");
}

将 PDF 文件转换为 PDF/A-4

将 PDF 转换为 PDF/A-4

Aspose.PDF for .NET 还支持将 PDF 文件转换为 PDF/A-4 格式的功能。

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfToPdfA4()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();
    
    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf"))
    {
        // If the document version is less than PDF-2.0, it must be converted to PDF-2.0
        document.Convert(Stream.Null, Aspose.Pdf.PdfFormat.v_2_0, Aspose.Pdf.ConvertErrorAction.Delete);
    
        // Convert to the PDF/A-4 format
        document.Convert(dataDir + "PDFA4ConversionLog.xml", Aspose.Pdf.PdfFormat.PDF_A_4, Aspose.Pdf.ConvertErrorAction.Delete);

        // Save PDF document
        document.Save(dataDir + "PDFToPDFA4_out.pdf");
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfToPdfA4()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();

    // Open PDF document
    using var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf");

    // If the document version is less than PDF-2.0, it must be converted to PDF-2.0
    document.Convert(Stream.Null, Aspose.Pdf.PdfFormat.v_2_0, Aspose.Pdf.ConvertErrorAction.Delete);

    // Convert to the PDF/A-4 format
    document.Convert(dataDir + "PDFA4ConversionLog.xml", Aspose.Pdf.PdfFormat.PDF_A_4, Aspose.Pdf.ConvertErrorAction.Delete);

    // Save PDF document
    document.Save(dataDir + "PDFToPDFA4_out.pdf");
}

向 PDF/A 文件添加附件

如果您需要向符合 PDF/A 的文档附加文件，则建议使用 Aspose.PDF.PdfFormat 枚举中的 PDF_A_3A 值。 PDF/A-3a 是提供将任何文件格式作为附件附加到符合 PDF/A 文件的格式。

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void AddAttachmentToPdfA()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();
    
    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf"))
    {
        // Setup new file to be added as attachment
        using (var fileSpecification = new Aspose.Pdf.FileSpecification(dataDir + "aspose-logo.jpg", "Large Image file"))
        {
            // Add attachment to document's attachment collection
            document.EmbeddedFiles.Add(fileSpecification);

            // Perform conversion to PDF/A-3a, so that the attachment is included in the resultant file
            document.Convert(dataDir + "PDFA3aConversionLog.xml", Aspose.Pdf.PdfFormat.PDF_A_3A, Aspose.Pdf.ConvertErrorAction.Delete);

            // Save PDF document
            document.Save(dataDir + "AddAttachmentToPDFA_out.pdf");
        }
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void AddAttachmentToPdfA()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();

    // Open PDF document
    using var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf");

    // Setup new file to be added as attachment
    using var fileSpecification = new Aspose.Pdf.FileSpecification(dataDir + "aspose-logo.jpg", "Large Image file");

    // Add attachment to document's attachment collection
    document.EmbeddedFiles.Add(fileSpecification);

    // Perform conversion to PDF/A-3a, so that the attachment is included in the resultant file
    document.Convert(dataDir + "PDFA3aConversionLog.xml", Aspose.Pdf.PdfFormat.PDF_A_3A, Aspose.Pdf.ConvertErrorAction.Delete);

    // Save PDF document
    document.Save(dataDir + "AddAttachmentToPDFA_out.pdf");
}

用替代字体替换缺失字体

根据 PDF/A 标准，字体应嵌入 PDF/A 文档中。然而，如果源文档中未嵌入字体且机器上不存在这些字体，则 PDF/A 转换将失败。在这种情况下，有必要用机器上存在的一些替代字体替换缺失的字体。在 PDF 转换为 PDF/A 的过程中，可以使用 SimpleFontSubsitution 类替换缺失的字体。

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ReplaceMissingFonts()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();

    try
    {
        // Check whether a font, used in the source document, is installed in the system
        Aspose.Pdf.Text.FontRepository.FindFont("AgencyFB");
    }
    catch (Aspose.Pdf.FontNotFoundException)
    {
        // Font is missing on the destination machine. Replace it with the Arial font installed in the system
        var fontSubstitution = new Aspose.Pdf.Text.SimpleFontSubstitution("AgencyFB", "Arial");
        Aspose.Pdf.Text.FontRepository.Substitutions.Add(fontSubstitution);
    }

    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf"))
    {
        // During the conversion, the missing font will be replaced with the substitution one
        document.Convert(dataDir + "ReplaceMissingFonts.xml", PdfFormat.PDF_A_1B, ConvertErrorAction.Delete);

        // Save PDF document
        document.Save(dataDir + "ReplaceMissingFonts_out.pdf");
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ReplaceMissingFonts()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();

    try
    {
        // Check whether a font, used in the source document, is installed in the system
        Aspose.Pdf.Text.FontRepository.FindFont("AgencyFB");
    }
    catch (Aspose.Pdf.FontNotFoundException)
    {
        // Font is missing on the destination machine. Replace it with the Arial font installed in the system
        var fontSubstitution = new Aspose.Pdf.Text.SimpleFontSubstitution("AgencyFB", "Arial");
        Aspose.Pdf.Text.FontRepository.Substitutions.Add(fontSubstitution);
    }

    // Open PDF document
    using var document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf");

    // During the conversion, the missing font will be replaced with the substitution one
    document.Convert(dataDir + "ReplaceMissingFonts.xml", PdfFormat.PDF_A_1B, ConvertErrorAction.Delete);

    // Save PDF document
    document.Save(dataDir + "ReplaceMissingFonts_out.pdf");
}

自动创建文档逻辑结构标签

PDF 文档可以包含逻辑结构标签，以增强可访问性和组织性。这些标签通过将文档内容划分为逻辑部分（如章节、段落等）来构建文档的结构。当文档转换为 PDF/A 时，Aspose.PDF 可以自动生成基本的逻辑结构标记。用户可以手动完善此结构，添加有关文档内容的进一步见解。

要生成逻辑文档结构，请创建 Aspose.Pdf.AutoTaggingSettings 类的实例，将其 AutoTaggingSettings.EnableAutoTagging 设置为 true，并将其分配给 PdfFormatConversionOptions.AutoTaggingSettings 属性。

如果文档已经具有逻辑结构标签，则启用自动标记将破坏现有的逻辑结构并生成一个新的结构。

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertToPdfAWithAutomaticTagging()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();

    // Open PDF document
    using (Aspose.Pdf.Document document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf"))
    {
        // Create conversion options
        Aspose.Pdf.PdfFormatConversionOptions options = new Aspose.Pdf.PdfFormatConversionOptions(dataDir + "ConvertToPdfAWithAutomaticTagging.xml", PdfFormat.PDF_A_1B, ConvertErrorAction.Delete);

        // Create auto-tagging settings
        // Aspose.Pdf.AutoTaggingSettings.Default may be used to set the same settings as given below
        Aspose.Pdf.AutoTaggingSettings autoTaggingSettings = new Aspose.Pdf.AutoTaggingSettings();

        // Enable auto-tagging during the conversion process
        autoTaggingSettings.EnableAutoTagging = true;

        // Use the heading recognition strategy that's optimal for the given document structure
        autoTaggingSettings.HeadingRecognitionStrategy = Aspose.Pdf.HeadingRecognitionStrategy.Auto;

        // Assign auto-tagging settings to be used during the conversion process
        options.AutoTaggingSettings = autoTaggingSettings;

        // During the conversion, the document logical structure will be automatically created
        document.Convert(options);

        // Save PDF document
        document.Save(dataDir + "ConvertToPdfAWithAutomaticTagging_out.pdf");
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertToPdfAWithAutomaticTagging()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_DocumentConversion();

    // Open PDF document
    using Aspose.Pdf.Document document = new Aspose.Pdf.Document(dataDir + "PDFToPDFA.pdf");

    // Create conversion options
    Aspose.Pdf.PdfFormatConversionOptions options = new Aspose.Pdf.PdfFormatConversionOptions(dataDir + "ConvertToPdfAWithAutomaticTagging.xml", PdfFormat.PDF_A_1B, ConvertErrorAction.Delete);

    // Create auto-tagging settings
    // Aspose.Pdf.AutoTaggingSettings.Default may be used to set the same settings as given below
    Aspose.Pdf.AutoTaggingSettings autoTaggingSettings = new Aspose.Pdf.AutoTaggingSettings
    {
        // Enable auto-tagging during the conversion process
        EnableAutoTagging = true,

        // Use the heading recognition strategy that's optimal for the given document structure
        HeadingRecognitionStrategy = Aspose.Pdf.HeadingRecognitionStrategy.Auto
    };

    // Assign auto-tagging settings to be used during the conversion process
    options.AutoTaggingSettings = autoTaggingSettings;

    // During the conversion, the document logical structure will be automatically created
    document.Convert(options);

    // Save PDF document
    document.Save(dataDir + "ConvertToPdfAWithAutomaticTagging_out.pdf");
}