Create, edit, or remove PDF annotations in UWP

After Nutrient UWP SDK loads annotations from a PDF, you can access them through the Document API.

The API returns a List of IAnnotation objects.
Each IAnnotation provides access to shared properties and methods, including:

Understanding the annotation bounding box

The BoundingBox defines the annotation’s location and size on the page. It’s represented by a Rect with:

X and Y describing the top-left coordinate of the annotation on the page.
Width and Height describing the size of the annotation.

Coordinate system

Nutrient UWP SDK and Nutrient Web SDK use the Instant JSON coordinate system:

The origin of the page, “0,0,” is at the top left.
The Y axis value increases as you move down the page.

To convert between the coordinate system above and the PDF coordinate system (where origin, “0,0,” is at the bottom left, with the Y axis value increasing as you move up the page), refer to the conversion utility methods guide.

Working with specific annotation types

Use the AnnotationType property to cast to a specific annotation type to work with its APIs:

if (annotation.AnnotationType == AnnotationType.Ink)
{
    var ink = annotation as AnnotationType.Ink;
    return ink.IsSignature;
}

Creating an annotation

To create an annotation on a page:

Instantiate the desired annotation type, as demonstrated in the code snippet below:

var textAnnot = new Text
{
    Contents = "A new text annotation",
    HorizontalAlign = HorizontalAlign.Right,
    VerticalAlign = VerticalAlign.Center,
    BoundingBox = new Rect(10, 10, 300, 300),
    FontSize = 48,
    Bold = true,
    Italic = true,
    FontColor = Colors.Cyan
};

Add the annotation to a page, as demonstrated in the code snippet below:

var createdTextAnnotation = await pdfView.Document.CreateAnnotationAsync(textAnnot);

Once added, the annotation will have a unique Id.

Updating an annotation

To update an existing annotation, use the code snippet below:

createdTextAnnotation.VerticalAlign = VerticalAlign.Top;
createdTextAnnotation.Opacity = 0.5f;
await pdfView.Document.UpdateAnnotationAsync(createdTextAnnotation);

Deleting an annotation

To delete an annotation, use the annotation’s Id to remove it, as demonstrated in the code snippet below:

await pdfView.Document.DeleteAnnotationAsync(createdTextAnnotation.Id);