Flatten PDF Annotations in C# .NET

Flattening a PDF annotation means that you remove the annotation object from a document’s internal structure and place its data directly on the PDF page as a regular content object. This means that the annotation is no longer editable and its data can’t be extracted.

To flatten an already existing annotation, use the GetAnnotationCount method to get the total number of annotations on the selected page, loop through all annotations on the selected page, and find the annotation that you want to flatten by any of its parameters, such as its title, type, or subject. Use the methods starting with the `GetAnnotation` prefix. The full list is available in the get properties guide.

To flatten a newly created annotation, use the following code:

using GdPicturePDF gdpicturePDF = new GdPicturePDF();
gdpicturePDF.LoadFromFile(@"C:\temp\source.pdf");
// Set the origin of the coordinate system.
gdpicturePDF.SetOrigin(PdfOrigin.PdfOriginTopLeft);
// Set the measurement unit to centimeters.
gdpicturePDF.SetMeasurementUnit(PdfMeasurementUnit.PdfMeasurementUnitCentimeter);
// Select the first PDF page.
gdpicturePDF.SelectPage(1);
// Set the text content and determine its size.
float fontSize = 16;
string fontResName = gdpicturePDF.AddStandardFont(PdfStandardFont.PdfStandardFontHelvetica);
string text = "Text annotation example.";
float textWidth = gdpicturePDF.GetTextWidth(fontResName, fontSize, text) + 0.5f;
float textHeight = gdpicturePDF.GetTextHeight(fontResName, fontSize, false) + 0.5f;
// Add the free text annotation.
int annotIndex = gdpicturePDF.AddFreeTextAnnotation(1, 2, textWidth, textHeight, true,
    "Annotation Example", "Example", text,
    fontResName, fontSize, 0, 0, 200, 100, 100, 100, 100);
// Flatten the free text annotation.
gdpicturePDF.FlattenAnnotation(annotIndex);
gdpicturePDF.SaveToFile(@"C:\temp\output.pdf");

Using gdpicturePDF As GdPicturePDF = New GdPicturePDF()
    gdpicturePDF.LoadFromFile("C:\temp\source.pdf")
    ' Set the origin of the coordinate system.
    gdpicturePDF.SetOrigin(PdfOrigin.PdfOriginTopLeft)
    ' Set the measurement unit to centimeters.
    gdpicturePDF.SetMeasurementUnit(PdfMeasurementUnit.PdfMeasurementUnitCentimeter)
    ' Select the first PDF page.
    gdpicturePDF.SelectPage(1)
    ' Set the text content and determine its size.
    Dim fontSize As Single = 16
    Dim fontResName As String = gdpicturePDF.AddStandardFont(PdfStandardFont.PdfStandardFontHelvetica)
    Dim text = "Text annotation example."
    Dim textWidth As Single = gdpicturePDF.GetTextWidth(fontResName, fontSize, text) + 0.5F
    Dim textHeight As Single = gdpicturePDF.GetTextHeight(fontResName, fontSize, False) + 0.5F
    ' Add the free text annotation.
    Dim annotIndex As Integer = gdpicturePDF.AddFreeTextAnnotation(1, 2, textWidth, textHeight, True, "Annotation Example", "Example", text, fontResName, fontSize, 0, 0, 200, 100, 100, 100, 100)
    ' Flatten the free text annotation.
    gdpicturePDF.FlattenAnnotation(annotIndex)
    gdpicturePDF.SaveToFile("C:\temp\output.pdf")
End Using

Used Methods

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