Annotations
using IronPdf;

// Create a new PDF or load and edit an existing document.
var pdf = PdfDocument.FromFile("existing.pdf");

int pageIndex1 = 0;
int pageIndex2 = 1;

// Create a PDF annotation object on a specified page index
var annotation1 = new IronPdf.Annotations.TextAnnotation(pageIndex1)
{
    Title = "This is the major title 1",
    Contents = "This is the long 'sticky note' comment 1st content...",
    X = 150,
    Y = 200,
    Width = 200,
    Height = 50,
    Opacity = 0.9,
    Printable = false,
    Hidden = false,
    OpenByDefault = true,
    ReadOnly = false,
    Rotatable = true
};

var annotation2 = new IronPdf.Annotations.TextAnnotation(pageIndex2)
{
    Title = "This is the major title 2",
    Contents = "This is the long 'sticky note' comment 2nd content...",
    X = 100,
    Y = 150,
    Width = 250,
    Height = 150,
    Opacity = 0.9,
    Printable = false,
    Hidden = false,
    OpenByDefault = true,
    ReadOnly = false,
    Rotatable = true
};

var annotation3 = new IronPdf.Annotations.TextAnnotation(pageIndex2)
{
    Title = "This is the major title 3",
    Contents = "This is the long 'sticky note' comment 3rd content...",
    X = 200,
    Y = 150,
    Width = 150,
    Height = 50,
    Opacity = 0.9,
    Printable = false,
    Hidden = false,
    OpenByDefault = true,
    ReadOnly = false,
    Rotatable = true
};

// Add the annotation "sticky note" within any new or existing PDF.
pdf.Annotations.Add(annotation1); // annotation1 index is 0.
pdf.Annotations.Add(annotation2); // annotation2 index is 1.
pdf.Annotations.Add(annotation3); // annotation3 index is 2.

// Remove a single annotation with specified index
pdf.Annotations.RemoveAt(1); // annotation2 is removed, annotation3 index becomes 1.

// Remove all annotaions on a specified page
pdf.Annotations.RemoveAllAnnotationsForPage(0); // remove all annotaion on page 1, annotation3 index becomes 0.

// Edit a single annotation with specified index
pdf.Annotations[0].Title = "new title for annotation 3";
pdf.Annotations[0].Contents = "This is new comment content of annotation 3";

// Remove all annotaions on the document
pdf.Annotations.Clear();

pdf.SaveAs("existing.pdf");
NuGet Download
PM > Install-Package IronPdf
Annotations

Annotations

PDF annotations allow "sticky note"-like comments to be added to PDF pages. The PdfDocument.Annotations.Add method and IronPdf.Annotations.TextAnnotation class allow annotations to be added programmatically. Advanced text annotation features supported include coloring, sizing, opacity, icons, and editing.

How to Add PDF Annotation in .NET

  1. Install C# library to add annotation to PDF.
  2. Open an existing or generate a new PDF in .NET.
  3. Create a TextAnnotation class and customize properties.
  4. Utilize the Annotations.Add method to add the newly created annotation to the PDF.
  5. Export the modified PDF to the desired folder.
Explore How to Add Annotations to PDFs with IronPDF
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