Annotate Text or Images in Documents

Empower your .NET Applications to Add, Edit & Remove all Popular Annotation Types from over 50 document formats for an Easier & Efficient Collaboration.

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.NET document annotation API

GroupDocs.Annotation for .NET


GroupDocs.Annotation for .NET is a comprehensive set of APIs that helps you build document annotation management applications in C#, ASP.NET and other related .NET technologies. You can create and work with all popular annotation types, such as area, point, text, ellipse, link, underline, polyline, arrow, distance, watermark, image etc for PDF, HTML, Microsoft Office Word, Excel spreadsheets, PowerPoint presentations, Visio, images, CAD drawing and various other formats. The document annotator library allows you to export documents after adding annotations, comments or highlighted notes back to its original format. It also gives you a handy set of data objects through which you can customize annotations as per your requirements.

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GroupDocs.Annotation for .NET Features



Add, Edit & Remove Annotations and Replies in Data Storage


Export Annotations from Data Storage to Document


Metered License – Controlled Billing by Paying According to API Usage


Assign User Access Rights to Restrict Annotation Activities on Document


Single Function Call to Fetch All Annotations of a Document


Assign Value to Point Annotation or Move Existing Point Value


Add Link Annotation to PDF, Word & PowerPoint Slides


Set Background Color of an Annotation or Remove all the Annotations from Document


Storage Independence via your own Data Storage or Default Inner “XML” Storage


Annotate PDF files with Accuracy – Get Image Representation of PDF Document & Cache Page Previews


Get Text Coordinates of Text Annotation in Image Representation of Document


Link User Comments to Area Annotation & Support for Nested Comments


Use Arrow Annotation for pointing to Particular Content


Use Distance Annotation to Draw a Line that Represents Distance among Objects


Point based Annotation that when Clicked Pops Window to Add Comments


Create a Connected Sequence of Line Segments Created as a Polyline Annotation


Create Straight Line Segments, Arc Segments, or a combination of the both


Mark Document Areas Proposed for Redaction


Add Image Annotation to PDF, Diagrams, Word, Excel, Presentations & Images


Add Text Field & Text based Stamp or Watermark in Document


Strike Through, Underline or Replace Particular Text in a Document


Resize Annotation by assigning new Height & Width Parameters


Get Thumbnails of Document Pages. Manage a Variety of Annotated Docs for Images & Diagrams


Export Annotations to & Work with Multi-page TIFF files


Adjust Vertical and Horizontal Alignment for Watermark Annotation


Add Text Horizontal Alignment for Text Field

Support for Multiple Types of Annotation

GroupDocs.Annotation for .NET enables you to work with various types of annotations. This gives freedom and ease of communication while collaborating with your team on tasks. You can use annotations, such as, area annotation (mark an area as rectangle and add notes to it), point annotation (stick comments at any point in document), text annotation (add comment to selected text), strikeout/underline annotation (applied to a paragraph), polyline annotation (draw shapes and freehand lines), arrow annotation (arrow pointer with attached comments), ellipse annotation (display text inside the ellipse), distance annotation (draw a line that represents distance among objects), link annotation (add web links to supported document formats), and watermark annotation (text stamp or watermark can be added in document).

Apply Text Annotation using C#

 // Initialize list of AnnotationInfo
List<AnnotationInfo> annotations = new List<AnnotationInfo>();
 // Initialize text annotation
AnnotationInfo textAnnotation = new AnnotationInfo
	Box = new Rectangle((float)265.44, (float)153.86, 206, 36), Type = AnnotationType.Text 
// Add annotation to list
// Get input file stream
Stream inputFile = new FileStream("D:/input.pdf", FileMode.Open, FileAccess.ReadWrite);
// Export annotation and save output file
CommonUtilities.SaveOutputDocument(inputFile, annotations, DocumentType.Pdf);

Properties used in Data Storage

GroupDocs.Annotation for .NET API provides a comprehensive set of data objects with properties, used in data storage. You can work with Annotation (coordinates, dimensions, type, color, frame style, background color etc.), Annotation Collaborator (ID, document, access rights etc.), Annotation Reply (reply, parent annotation, GUID, message, time etc.), Document (GUID, name, owner, type, access rights etc.), User (ID, nick, email, password, photo etc.).

Access Rights Management

GroupDocs.Annotation for .NET API offers easy way to manage access rights of annotations. The properties that you can assign or revoke include View, Annotate, Download, Export, Delete etc.

Support and Learning Resources


GroupDocs.Annotation offers document automation APIs for other popular development environments as listed below: