.NET APIs to annotate and export annotated documents

.NET document annotation API to manage annotated notes, comments and tags to documents content within your applications

  Download Free Trial
.NET document annotation API

GroupDocs.Annotation for .NET


GroupDocs.Annotation for .NET API allows developers to seamlessly enhance their applications with the capability to annotate text or images in a document. Annotation can be applied in form of comments, explanations with highlighted notes, watermark, polyline and much more. Annotator API supports PDF, Microsoft Word DOCX, Excel XLSX and PowerPoint PPTX documents.

How to Annotate – Using GroupDocs.Annotation for .NET API annotations are created and rendered in a separate layer over displayed documents, so that original files are not modified. They can be stored as a set of JSON files or in a DB, as well as merged with the original file and exported to PDF or Word document.

Advanced Document Annotation API Features



Annotate any PDF, DOCX, XLSX and PPTX documents


Multiple markup and commenting tools


Reply based comments


Highlight Text Annotation


Custom stamp Annotation


Threading in comments


Simultaneous document annotations by multiple users


Save annotations in different objects like JSON files, Databases or merge with original file


Export annotations to separate PDF or Word file


Abstract storage option – achieve it by using implemented interface provided by API


User Management – Abstract-ready user management


Annotation Compatibility - Annotations added are compatible with native PDF annotations

Core Annotations – markup and commenting tools

  • Area Annotation – Mark an area for annotation in form of notes. Area can be a line, paragraph or portion of document
  • Point Annotation – attach comments to any point
  • Text Annotation – add explanation to any selected text

Add text annotation - 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
// Export annotation and save output file
CommonUtilities.SaveOutputDocument("input.pdf", annotations, DocumentType.Pdf);
  • Strikeout / Underline Annotation – mark up text or revision instructions by editors with Strikeout or underline
  • Text replacement -Replace selected text
  • Text and Area redaction – blackout selected text and area within the document
  • Polyline – draw shapes and lines.
  • Pointer/arrow – attach arrows with notes
  • Watermark – add a watermark
  • Ruler or Distance Annotation – measure the distance between objects
  • Undo/redo – cancel or reverse annotations

Installation and Usage

API can be consumed on .NET Framework starting from V2.0 and Mono Framework starting from V1.2. Annotation API files can be installed/downloaded using following smooth ways

Support and Learning Resources


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