Namespace IronPdf.Annotations

Classes

LinkAnnotation

Creates a clickable link annotation that navigates to a specific page within the same PDF document. Useful for building custom tables of contents, cross-references, and in-document navigation.

// Add a link on page 0 that navigates to page 5:
var link = new LinkAnnotation(pageIndex: 0, destinationPageIndex: 5)
{
    X = 50, Y = 700,
    Width = 200, Height = 20
};
pdf.Annotations.Add(link);

// Custom TOC link with color:
var tocLink = new LinkAnnotation(0, 3)
{
    X = 72, Y = 600,
    Width = 300, Height = 16,
    Contents = "Chapter 1 - Introduction"
};
pdf.Annotations.Add(tocLink);

The link annotation creates an invisible clickable region on the page.

See: https://ironpdf.com/how-to/annotations/

Coordinate note: The Y property sets the bottom edge

of the clickable area using PDF coordinates (origin at bottom-left of page). When positioning

links over existing text using PdfPage.TextChunks, use BoundingBox.Bottom for Y and Math.Abs(BoundingBox.Top - BoundingBox.Bottom) for Height.

PdfAnnotation

Base PDF annotation

PdfAnnotationCollection

Manages the collection of annotations (sticky notes, comments) in a PDF document. Supports adding, removing, and iterating through annotations across all pages.

Access via Annotations property. Changes to the collection are automatically synchronized with the PDF document.

Example - Work with annotations:

var pdf = PdfDocument.FromFile("document.pdf");
// Add annotation to first page:
var note = new TextAnnotation(0)
{
Title = "Review Note",
Contents = "Please verify this section",
X = 100,
Y = 700
};
pdf.Annotations.Add(note);
// List all annotations:
foreach (var annotation in pdf.Annotations)
Console.WriteLine($"Page {annotation.PageIndex}: {annotation.Contents}");
// Remove annotations from page 2:
pdf.Annotations.RemoveAllAnnotationsForPage(1);
// Clear all annotations:
pdf.Annotations.Clear();
pdf.SaveAs("annotated.pdf");

PdfAnnotationType

PdfFreeTextAnnotation

PDF free annotation

PdfLinkAnnotation

PDF link annotation

PdfTextAnnotation

PDF text annotation

PdfUnknownAnnotation

An annotation whose subtype has no dedicated representation, for example a form-field Widget. Only the common annotation fields (Type, Rectangle, Color, Name, Contents, Hidden) are populated. Returning this rather than throwing lets callers that enumerate a page's annotations, such as the page-numbered Table of Contents scan, safely ignore subtypes they do not handle.

TextAnnotation

Creates interactive sticky-note annotations for PDF documents - like Post-it® notes for digital documents. Perfect for comments, review feedback, and collaborative document workflows.

// Add simple comment:
var comment = new TextAnnotation(0, "Review", "Please check figures") {
    X = 100, Y = 100,
    Color = Color.Yellow
};
pdf.Annotations.Add(comment);

// Review annotation with metadata:
var review = new TextAnnotation(pageIndex: 0) {
    Title = "John Smith",
    Subject = "Technical Review",
    Contents = "Algorithm needs optimization",
    X = 300, Y = 500,
    Color = Color.Red,
    OpenByDefault = true
};
pdf.Annotations.Add(review);

// Hidden annotation for metadata:
var metadata = new TextAnnotation(0, "Version", "v2.1.0") {
    Hidden = true,
    Printable = false
};
pdf.Annotations.Add(metadata);

Annotations appear as icons that expand to show full text

Some PDF viewers may not respect all properties

See: https://ironpdf.com/how-to/annotations/

TextAnnotation.AnnotationIcon

Icons used to interact with (open/close) the annotation with the PDF page.

Interfaces

IAnnotation

PDF document annotation