编辑 PDF 文件标签

标记 PDF 旨在通过为每个元素（如文本、图像和链接）标记定义其目的和角色的标签来确保可访问性。在编辑这些 PDF 时，保持这些标签至关重要，以确保符合 WCAG 等可访问性标准。

像 Aspose.PDF for .NET 这样的工具提供了处理标记内容的强大功能，但必须小心维护文档的结构和可访问性。通过系统地为图像添加替代文本或格式化段落，标记 PDF 保持可访问性和用户友好性。

自 24.7 版本发布以来，作为编辑标记 PDF 的一部分，添加了 Aspose.Pdf.LogicalStructure.Element 上的方法：

• Tag（为特定操作符（如图像、文本和链接）添加标签）。
• InsertChild。
• RemoveChild。
• ClearChilds。

这些方法允许您编辑 PDF 文件标签，例如：

.NET Core 3.1

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

    // Open PDF document
    using (var document = new Aspose.Pdf.Document(dataDir + "EditTags.pdf"))
    {
        // Get first page 
        var page = document.Pages[1];
        // The marked content operator on page for the image.
        Aspose.Pdf.Operators.BDC imageBdc = null;
        // The marked content operator on page for the text.
        Aspose.Pdf.Operators.BDC text1BDC = null;
        // The marked content operator on page for the link1.
        Aspose.Pdf.Operators.BDC link1Bdc = null;
        // The marked content operator on page for the link2.
        Aspose.Pdf.Operators.BDC link2Bdc = null;
        // The marked content operator on page for the Hello text.
        Aspose.Pdf.Operators.BDC helloBdc = null;
        // Find the marked content operators for the elements on the page.
        for (int i = 1; i <= page.Contents.Count; i++)
        {
            Aspose.Pdf.Operator op = page.Contents[i];
            var bdc = op as Aspose.Pdf.Operators.BDC;
            if (bdc != null)
            {
                // The text operator with marked content id = 0 was found.
                if (bdc.Properties.MCID == 0)
                {
                    helloBdc = bdc;
                }
            }

            var doXobj = op as Aspose.Pdf.Operators.Do;
            if (doXobj != null)
            {
                // Wrap the image XObject with makred content operator.
                imageBdc = new Aspose.Pdf.Operators.BDC("Figure");
                page.Contents.Insert(i - 2, imageBdc);
                i++;
                page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
                i++;
            }

            var tx = op as Aspose.Pdf.Operators.TextShowOperator;
            if (tx != null)
            {
                // Wrap the text operator on page with makred content operator.
                if (tx.Text.Contains("efter Ukendt forfatter er licenseret under"))
                {
                    text1BDC = new Aspose.Pdf.Operators.BDC("P");
                    page.Contents.Insert(i - 1, text1BDC);
                    i++;
                    page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
                    i++;
                }
                // Wrap the text operator on page with makred content operator.
                if (tx.Text.Contains("CC"))
                {
                    link1Bdc = new Aspose.Pdf.Operators.BDC("Link");
                    page.Contents.Insert(i - 1, link1Bdc);
                    i++;
                    page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
                    i++;
                }
                // Wrap the text operator on page with makred content operator.
                if (tx.Text.Contains("Dette billede"))
                {
                    link2Bdc = new Aspose.Pdf.Operators.BDC("Link");
                    page.Contents.Insert(i - 1, link2Bdc);
                    i++;
                    page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
                    i++;
                }
            }
        }

        Aspose.Pdf.Tagged.ITaggedContent tagged = document.TaggedContent;

        // Find exist struct element in document.
        Aspose.Pdf.LogicalStructure.Element helloParagraph = tagged.RootElement.ChildElements[1];

        // Clear the subtree of an existing structure tree element.
        helloParagraph.ClearChilds();

        // Tag paragraph struct element to text on page.
        Aspose.Pdf.LogicalStructure.MCRElement helloMCR = helloParagraph.Tag(helloBdc);

        // Get the struct element attributes.
        Aspose.Pdf.LogicalStructure.StructureAttributes helloAttrs = helloMCR.ParentStructureElement.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

        // Fill the paragraph struct element spaceAfter attribute.
        var helloSpaceAfter = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.SpaceAfter);
        helloSpaceAfter.SetNumberValue(30.625);
        helloAttrs.SetAttribute(helloSpaceAfter);

        // Create a figure element and place it to root element in second position.
        Aspose.Pdf.LogicalStructure.FigureElement figure = tagged.CreateFigureElement();
        tagged.RootElement.InsertChild(figure, 2);

        // Set an alternative text for the figure.
        figure.AlternativeText = "A fly.";

        // Tag figure struct element to image element on page.
        Aspose.Pdf.LogicalStructure.MCRElement figureMCR = figure.Tag(imageBdc);

        // Get the figure struct element attributes.
        Aspose.Pdf.LogicalStructure.StructureAttributes figureAttrs = figureMCR.ParentStructureElement.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

        // Fill the figure struct element spaceAfter attribute.
        var figureSpaceAfter = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.SpaceAfter);
        figureSpaceAfter.SetNumberValue(3.625);
        figureAttrs.SetAttribute(figureSpaceAfter);

        // Fill the figure struct element BBox attribute.
        var figureBBox = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.BBox);
        figureBBox.SetArrayNumberValue(new double?[] { 71.9971, 375.839, 523.299, 714.345 });
        figureAttrs.SetAttribute(figureBBox);

        // Fill the figure struct element placement attribute.
        var figurePlacement = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.Placement);
        figurePlacement.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.Placement_Block);
        figureAttrs.SetAttribute(figurePlacement);

        // Find exist struct element in document.
        Aspose.Pdf.LogicalStructure.Element p2 = (Aspose.Pdf.LogicalStructure.StructureElement)tagged.RootElement.ChildElements[3];

        // Clear the subtree of an existing structure tree element.
        p2.ClearChilds();

        // Create the span struct element.
        Aspose.Pdf.LogicalStructure.SpanElement span1 = tagged.CreateSpanElement();

        // Get the span1 struct element attributes.
        Aspose.Pdf.LogicalStructure.StructureAttributes span1Attrs = span1.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

        // Fill the span1 struct element textDecorationType attribute.
        var span1TextDecorationType = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationType);
        span1TextDecorationType.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.TextDecorationType_Underline);
        span1Attrs.SetAttribute(span1TextDecorationType);

        // Fill the span1 struct element textDecorationThickness attribute.
        var span1TextDecorationThickness = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationThickness);
        span1TextDecorationThickness.SetNumberValue(0);
        span1Attrs.SetAttribute(span1TextDecorationThickness);

        // Fill the span1 struct element textDecorationColor attribute.
        var span1TextDecorationColor = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationColor);
        span1TextDecorationColor.SetArrayNumberValue(new double?[] { 0.0196075, 0.384308, 0.756866 });
        span1Attrs.SetAttribute(span1TextDecorationColor);

        // Append the span element to the paragraph element in the struct tree.
        p2.AppendChild(span1);

        // Tag paragraph struct element to text element on page.
        Aspose.Pdf.LogicalStructure.MCRElement text1MCR = p2.Tag(text1BDC);

        // Get the mcr struct element attributes.
        Aspose.Pdf.LogicalStructure.StructureAttributes text1Attrs = text1MCR.ParentStructureElement.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

        // Fill the text1 MCR struct element textAlign attribute.
        var text1TextAlign = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextAlign);
        text1TextAlign.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.TextAlign_Center);
        text1Attrs.SetAttribute(text1TextAlign);

        // Create the span struct element.
        Aspose.Pdf.LogicalStructure.SpanElement span2 = tagged.CreateSpanElement();

        // Get the span2 struct element attributes.
        Aspose.Pdf.LogicalStructure.StructureAttributes span2Attrs = span2.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

        // Fill the span2 struct element textDecorationType attribute.
        var textDecorationType = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationType);
        textDecorationType.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.TextDecorationType_Underline);
        span2Attrs.SetAttribute(textDecorationType);

        // Fill the span2 struct element textDecorationThickness attribute.
        var textDecorationThickness = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationThickness);
        textDecorationThickness.SetNumberValue(0);
        span2Attrs.SetAttribute(textDecorationThickness);

        // Fill the span2 struct element textDecorationColor attribute.
        var textDecorationColor = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationColor);
        textDecorationColor.SetArrayNumberValue(new double?[] { 0.0196075, 0.384308, 0.756866 });
        span2Attrs.SetAttribute(textDecorationColor);

        // Append the span struct element to the struct element tree.
        p2.AppendChild(span2);

        // Create the link struct element.
        Aspose.Pdf.LogicalStructure.LinkElement link2 = tagged.CreateLinkElement();
        // Set an id attribute of struct element.
        link2.SetId(Guid.NewGuid().ToString());
        // Append the link struct element to the struct element tree.
        span2.AppendChild(link2);
        // Tag link struct element to the page annotation element.
        link2.Tag(page.Annotations[1]);
        // Tag link struct element to text element on page.
        link2.Tag(link2Bdc);

        // Create the link struct element.
        Aspose.Pdf.LogicalStructure.LinkElement link1 = tagged.CreateLinkElement();
        // Set an id attribute of struct element.
        link1.SetId(Guid.NewGuid().ToString());
        // Append the link struct element to the struct element tree.
        span1.AppendChild(link1);
        // Tag link struct element to the page annotation element.
        link1.Tag(page.Annotations[2]);
        // Tag link struct element to text element on page.
        link1.Tag(link1Bdc);

        // Remove the struct element at index 0 from the struct tree.
        tagged.RootElement.RemoveChild(0);

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

.NET 8

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

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

    // Get first page
    var page = document.Pages[1];
    // The marked content operator on page for the image.
    Aspose.Pdf.Operators.BDC imageBdc = null;
    // The marked content operator on page for the text.
    Aspose.Pdf.Operators.BDC text1BDC = null;
    // The marked content operator on page for the link1.
    Aspose.Pdf.Operators.BDC link1Bdc = null;
    // The marked content operator on page for the link2.
    Aspose.Pdf.Operators.BDC link2Bdc = null;
    // The marked content operator on page for the Hello text.
    Aspose.Pdf.Operators.BDC helloBdc = null;
    // Find the marked content operators for the elements on the page.
    for (int i = 1; i <= page.Contents.Count; i++)
    {
        Aspose.Pdf.Operator op = page.Contents[i];
        var bdc = op as Aspose.Pdf.Operators.BDC;
        if (bdc != null)
        {
            // The text operator with marked content id = 0 was found.
            if (bdc.Properties.MCID == 0)
            {
                helloBdc = bdc;
            }
        }

        var doXobj = op as Aspose.Pdf.Operators.Do;
        if (doXobj != null)
        {
            // Wrap the image XObject with makred content operator.
            imageBdc = new Aspose.Pdf.Operators.BDC("Figure");
            page.Contents.Insert(i - 2, imageBdc);
            i++;
            page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
            i++;
        }

        var tx = op as Aspose.Pdf.Operators.TextShowOperator;
        if (tx != null)
        {
            // Wrap the text operator on page with makred content operator.
            if (tx.Text.Contains("efter Ukendt forfatter er licenseret under"))
            {
                text1BDC = new Aspose.Pdf.Operators.BDC("P");
                page.Contents.Insert(i - 1, text1BDC);
                i++;
                page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
                i++;
            }
            // Wrap the text operator on page with makred content operator.
            if (tx.Text.Contains("CC"))
            {
                link1Bdc = new Aspose.Pdf.Operators.BDC("Link");
                page.Contents.Insert(i - 1, link1Bdc);
                i++;
                page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
                i++;
            }
            // Wrap the text operator on page with makred content operator.
            if (tx.Text.Contains("Dette billede"))
            {
                link2Bdc = new Aspose.Pdf.Operators.BDC("Link");
                page.Contents.Insert(i - 1, link2Bdc);
                i++;
                page.Contents.Insert(i + 1, new Aspose.Pdf.Operators.EMC());
                i++;
            }
        }
    }

    Aspose.Pdf.Tagged.ITaggedContent tagged = document.TaggedContent;

    // Find exist struct element in document.
    Aspose.Pdf.LogicalStructure.Element helloParagraph = tagged.RootElement.ChildElements[1];

    // Clear the subtree of an existing structure tree element.
    helloParagraph.ClearChilds();

    // Tag paragraph struct element to text on page.
    Aspose.Pdf.LogicalStructure.MCRElement helloMCR = helloParagraph.Tag(helloBdc);

    // Get the struct element attributes.
    Aspose.Pdf.LogicalStructure.StructureAttributes helloAttrs = helloMCR.ParentStructureElement.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

    // Fill the paragraph struct element spaceAfter attribute.
    var helloSpaceAfter = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.SpaceAfter);
    helloSpaceAfter.SetNumberValue(30.625);
    helloAttrs.SetAttribute(helloSpaceAfter);

    // Create a figure element and place it to root element in second position.
    Aspose.Pdf.LogicalStructure.FigureElement figure = tagged.CreateFigureElement();
    tagged.RootElement.InsertChild(figure, 2);

    // Set an alternative text for the figure.
    figure.AlternativeText = "A fly.";

    // Tag figure struct element to image element on page.
    Aspose.Pdf.LogicalStructure.MCRElement figureMCR = figure.Tag(imageBdc);

    // Get the figure struct element attributes.
    Aspose.Pdf.LogicalStructure.StructureAttributes figureAttrs = figureMCR.ParentStructureElement.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

    // Fill the figure struct element spaceAfter attribute.
    var figureSpaceAfter = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.SpaceAfter);
    figureSpaceAfter.SetNumberValue(3.625);
    figureAttrs.SetAttribute(figureSpaceAfter);

    // Fill the figure struct element BBox attribute.
    var figureBBox = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.BBox);
    figureBBox.SetArrayNumberValue(new double?[] { 71.9971, 375.839, 523.299, 714.345 });
    figureAttrs.SetAttribute(figureBBox);

    // Fill the figure struct element placement attribute.
    var figurePlacement = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.Placement);
    figurePlacement.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.Placement_Block);
    figureAttrs.SetAttribute(figurePlacement);

    // Find exist struct element in document.
    Aspose.Pdf.LogicalStructure.Element p2 = (Aspose.Pdf.LogicalStructure.StructureElement)tagged.RootElement.ChildElements[3];

    // Clear the subtree of an existing structure tree element.
    p2.ClearChilds();

    // Create the span struct element.
    Aspose.Pdf.LogicalStructure.SpanElement span1 = tagged.CreateSpanElement();

    // Get the span1 struct element attributes.
    Aspose.Pdf.LogicalStructure.StructureAttributes span1Attrs = span1.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

    // Fill the span1 struct element textDecorationType attribute.
    var span1TextDecorationType = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationType);
    span1TextDecorationType.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.TextDecorationType_Underline);
    span1Attrs.SetAttribute(span1TextDecorationType);

    // Fill the span1 struct element textDecorationThickness attribute.
    var span1TextDecorationThickness = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationThickness);
    span1TextDecorationThickness.SetNumberValue(0);
    span1Attrs.SetAttribute(span1TextDecorationThickness);

    // Fill the span1 struct element textDecorationColor attribute.
    var span1TextDecorationColor = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationColor);
    span1TextDecorationColor.SetArrayNumberValue(new double?[] { 0.0196075, 0.384308, 0.756866 });
    span1Attrs.SetAttribute(span1TextDecorationColor);

    // Append the span element to the paragraph element in the struct tree.
    p2.AppendChild(span1);

    // Tag paragraph struct element to text element on page.
    Aspose.Pdf.LogicalStructure.MCRElement text1MCR = p2.Tag(text1BDC);

    // Get the mcr struct element attributes.
    Aspose.Pdf.LogicalStructure.StructureAttributes text1Attrs = text1MCR.ParentStructureElement.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

    // Fill the text1 MCR struct element textAlign attribute.
    var text1TextAlign = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextAlign);
    text1TextAlign.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.TextAlign_Center);
    text1Attrs.SetAttribute(text1TextAlign);

    // Create the span struct element.
    Aspose.Pdf.LogicalStructure.SpanElement span2 = tagged.CreateSpanElement();

    // Get the span2 struct element attributes.
    Aspose.Pdf.LogicalStructure.StructureAttributes span2Attrs = span2.Attributes.CreateAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);

    // Fill the span2 struct element textDecorationType attribute.
    var textDecorationType = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationType);
    textDecorationType.SetNameValue(Aspose.Pdf.LogicalStructure.AttributeName.TextDecorationType_Underline);
    span2Attrs.SetAttribute(textDecorationType);

    // Fill the span2 struct element textDecorationThickness attribute.
    var textDecorationThickness = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationThickness);
    textDecorationThickness.SetNumberValue(0);
    span2Attrs.SetAttribute(textDecorationThickness);

    // Fill the span2 struct element textDecorationColor attribute.
    var textDecorationColor = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.TextDecorationColor);
    textDecorationColor.SetArrayNumberValue(new double?[] { 0.0196075, 0.384308, 0.756866 });
    span2Attrs.SetAttribute(textDecorationColor);

    // Append the span struct element to the struct element tree.
    p2.AppendChild(span2);

    // Create the link struct element.
    Aspose.Pdf.LogicalStructure.LinkElement link2 = tagged.CreateLinkElement();
    // Set an id attribute of struct element.
    link2.SetId(Guid.NewGuid().ToString());
    // Append the link struct element to the struct element tree.
    span2.AppendChild(link2);
    // Tag link struct element to the page annotation element.
    link2.Tag(page.Annotations[1]);
    // Tag link struct element to text element on page.
    link2.Tag(link2Bdc);

    // Create the link struct element.
    Aspose.Pdf.LogicalStructure.LinkElement link1 = tagged.CreateLinkElement();
    // Set an id attribute of struct element.
    link1.SetId(Guid.NewGuid().ToString());
    // Append the link struct element to the struct element tree.
    span1.AppendChild(link1);
    // Tag link struct element to the page annotation element.
    link1.Tag(page.Annotations[2]);
    // Tag link struct element to text element on page.
    link1.Tag(link1Bdc);

    // Remove the struct element at index 0 from the struct tree.
    tagged.RootElement.RemoveChild(0);

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