Create an annotation in a PDF using C#

To create an annotation in a PDF document, follow the steps below:

Create a GdPicturePDF object.
Load the PDF file with the LoadFromFile method.
Set the origin of the coordinate system with the SetOrigin method. This method requires the PDFOrigin enumeration.
Set the measurement unit with the SetMeasurementUnit method to specify the annotation’s dimensions and position. This method uses the PdfMeasurementUnit enumeration.
Select the PDF page where you want to place the annotation using the SelectPage method.
Optional: Specify the font type. For more information, refer to the Font Type section of the guide on adding text to PDFs.
Add the annotation with any of the following methods:
Save the PDF document to a file with the SaveToFile method.

All methods that create a new annotation return an integer value, which is the annotation’s index. Recommended: Save the annotation index to a variable so that you can later reference that annotation.

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);
float textHeight = gdpicturePDF.GetTextHeight(fontResName, fontSize, false);
// Add the free text annotation.
int annotIndex = gdpicturePDF.AddFreeTextAnnotation(1, 2, textWidth + 0.5f, textHeight + 0.5f, true,
    "Annotation Example", "Example", text,
    fontResName, fontSize, 0, 0, 200, 100, 100, 100, 100);
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)
    Dim textHeight As Single = gdpicturePDF.GetTextHeight(fontResName, fontSize, False)
    ' Add the free text annotation.
    Dim annotIndex As Integer = gdpicturePDF.AddFreeTextAnnotation(1, 2, textWidth + 0.5F, textHeight + 0.5F, True,
        "Annotation Example", "Example", text,
        fontResName, fontSize, 0, 0, 200, 100, 100, 100, 100)
    gdpicturePDF.SaveToFile("C:\temp\output.pdf")
End Using

Used methods

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