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Line Annotation (Shape) in React PDF Viewer

27 Feb 20267 minutes to read

Line annotations allow users to draw straight connectors or callouts on PDFs for markup, review, diagrams, or measurement guides. They support customization of color, thickness, opacity, and arrowheads, and can be edited, resized, deleted, or exported along with the document.

Line overview

Enable Line Annotation in the Viewer

To enable Line annotations, inject the following modules into the React PDF Viewer:

import * as React from 'react';
import * as ReactDOM from 'react-dom/client';
import { PdfViewerComponent, Inject, Toolbar, Annotation } from '@syncfusion/ej2-react-pdfviewer';

function App() {
  return (
    <PdfViewerComponent
      id="container"
      documentPath="https://cdn.syncfusion.com/content/pdf/pdf-succinctly.pdf"
      resourceUrl="https://cdn.syncfusion.com/ej2/31.2.2/dist/ej2-pdfviewer-lib"
      style={{ height: '650px' }}
    >
      <Inject services={[Toolbar, Annotation]} />
    </PdfViewerComponent>
  );
}

ReactDOM.createRoot(document.getElementById('sample')).render(<App />);

Add Line Annotation

Add Line Annotation Using the Toolbar

  1. Open the Annotation Toolbar.
  2. Select Shapes → Line.
  3. Click and drag on the PDF page to draw the line.

Shape toolbar

NOTE

When in Pan mode, selecting a shape tool automatically switches the viewer to selection mode for smooth interaction.

Enable Line Mode

Switch the viewer into highlight mode using setAnnotationMode('Line').

function enableLineMode() {
  const viewer = document.getElementById('container').ej2_instances[0];
  viewer.annotation.setAnnotationMode('Line');
}

Exit Line Mode

Switch back to normal mode using:

function exitLineMode() {
  const viewer = document.getElementById('container').ej2_instances[0];
  viewer.annotation.setAnnotationMode('None');
}

Add Line Programmatically

You can add line annotations using the addAnnotation API.

function addLine() {
  const viewer = document.getElementById('container').ej2_instances[0];
  viewer.annotation.addAnnotation('Line', {
    offset: { x: 200, y: 230 },
    pageNumber: 1,
    vertexPoints: [
      { x: 200, y: 230 },
      { x: 350, y: 230 }
    ]
  });
}

Customize Line Appearance

Configure default line appearance using the lineSettings property.

<PdfViewerComponent
  id="container"
  documentPath="https://cdn.syncfusion.com/content/pdf/pdf-succinctly.pdf"
  resourceUrl="https://cdn.syncfusion.com/ej2/31.2.2/dist/ej2-pdfviewer-lib"
  lineSettings={{ strokeColor: '#0066ff', thickness: 2, opacity: 0.9 }}
  style={{ height: '650px' }}
>
  <Inject services={[Toolbar, Annotation]} />
</PdfViewerComponent>

NOTE

Fill color is available only when an arrowhead style is applied at the Start or End of the line. If both are set to None, the Fill option is disabled.

Manage Line (Edit, Move, Resize, Delete)

Edit Line

Edit Line Appearance (UI)

  • Select a line to view resize handles.
  • Drag endpoints to adjust length/angle.
  • Edit stroke color, opacity, and thickness using the annotation toolbar.

Shape tools

Use the annotation toolbar:

  • Edit Color tool
    Edit color

  • Edit Opacity slider
    Edit opacity

  • Line Properties
    Open the Line Properties dialog via Right Click → Properties.

Line properties dialog

Edit Line Programmatically

Modify an existing Line programmatically using editAnnotation().

function editLineProgrammatically() {
  const viewer = document.getElementById('container').ej2_instances[0];
  for (const annot of viewer.annotationCollection) {
    if (annot.subject === 'Line') {
      annot.strokeColor = '#ff0000';
      annot.thickness = 3;
      viewer.annotation.editAnnotation(annot);
      break;
    }
  }
}

Delete Line

The PDF Viewer supports deleting existing annotations through the UI and API.
See Delete Annotation for full behavior and workflows.

Comments

Use the Comments panel to add, view, and reply to threaded discussions linked to line annotations. It provides a dedicated interface for collaboration and review within the PDF Viewer.

Set properties while adding Individual Annotation

Set properties for individual line annotations using the lineSettings API or by passing per‑annotation values during addAnnotation.

function addMultipleLines() {
  const viewer = document.getElementById('container').ej2_instances[0];

  // Line 1
  viewer.annotation.addAnnotation('Line', {
    offset: { x: 200, y: 230 },
    pageNumber: 1,
    vertexPoints: [
      { x: 200, y: 230 },
      { x: 350, y: 230 }
    ],
    strokeColor: '#0066ff',
    thickness: 2,
    opacity: 0.9,
    author: 'User 1'
  });

  // Line 2
  viewer.annotation.addAnnotation('Line', {
    offset: { x: 220, y: 300 },
    pageNumber: 1,
    vertexPoints: [
      { x: 220, y: 300 },
      { x: 400, y: 300 }
    ],
    strokeColor: '#ff1010',
    thickness: 3,
    opacity: 0.9,
    author: 'User 2'
  });
}

Disable Line Annotation

Disable shape annotations (Line, Arrow, Rectangle, Circle, Polygon) using the enableShapeAnnotation property.

<PdfViewerComponent
  id="container"
  enableShapeAnnotation={false}
  documentPath="https://cdn.syncfusion.com/content/pdf/pdf-succinctly.pdf"
  resourceUrl="https://cdn.syncfusion.com/ej2/31.2.2/dist/ej2-pdfviewer-lib"
  style={{ height: '650px' }}
>
  <Inject services={[Toolbar, Annotation]} />
</PdfViewerComponent>

Handle Line Events

The PDF viewer provides annotation life-cycle events that notify when Line annotations are added, modified, selected, or removed.
For the full list of available events and their descriptions, see Annotation Events

Export and Import

The PDF Viewer supports exporting and importing annotations. For details on supported formats and workflows, see Export and Import annotations.

See Also