Adding Comments and Replies in Our JavaScript PDF Viewer

As of PSPDFKit for Web 2020.1, PSPDFKit provides user interface (UI) components for viewing, adding, and deleting comments in PDF documents. This component, Instant Comments, is available only if you’re using PSPDFKit Instant.

You can use Instant Comments to build collaborative workflows where multiple users can discuss specific sections of a document without leaving the viewer. The PSPDFKit Instant engine allows users to receive updates in real time.


Instant Comments is a separate component in your PSPDFKit license. Without this included in your license, your app won’t be able to view, search, or add comments. Please contact our Sales team to add Instant Comments to your license.

If you’re a new customer, you can try Instant Comments without a license key. If you’re an existing customer, please ask our Sales team for a trial license if you’re interested.


Before continuing, it’s helpful to first define some terminology as it relates to Instant Comments:

  • root annotation — This is the annotation to which all the comments in a single thread are linked.

  • comment thread — This is a group of comments with the same root annotation.

  • comment — This is a single comment added by any user.


All comments are linked to their respective root annotations. The comments with the same root annotation are part of a single comment thread. There can be two types of root annotations:

  • MarkupAnnotation — You can start a new comment thread by selecting some text and clicking on comment icon in the markup annotation inline toolbar. In this case, the markup annotation created will act as a root annotation.

  • CommentMarkerAnnotation — A comment marker annotation is a new annotation that can be added anywhere in a PDF document and used to start comment threads.

Getting Started

By default, we don’t show the comment tool (comment icon) in the main toolbar. This is because we want you to think about the workflow you want for your users and then decide whether or not you want to add it in the main toolbar. For example, if you want to allow the creation of comments from the main toolbar and disable sticky notes, you can do the following:

const toolbarItems = PSPDFKit.defaultToolbarItems
	.concat({ type: 'comment' }) // Add comment tool.
	.filter((item) => item.type !== 'note'); // Remove note tool.

	// ...

Note that you’ll have to add the comment tool in the main toolbar if you want to add comments using comment markers.

Adding a Comment

Since there are two types of root annotations, there are two ways you can add comments with the user interface.

From the Main Toolbar

Comment Main Toolbar

This method involves the creation of CommentMarkerAnnotation before the creation of comments. To add a comment marker, you first need to click on the comment tool (comment icon) in the main toolbar and then choose a destination on the page where you want to add your comment marker. Once you click on the destination, you’ll see a comment editor where you can add your first comment and start a new thread.

Using Markup Annotations

Comment Inline Toolbar

If you want to add a comment linked to a text annotation, you can do it using the markup annotation. To do this, create a new markup annotation and click on the comment tool (comment icon) in the inline toolbar. Afterward, you’ll see a comment editor where you can add your first comment and start the new thread.

Note that, at the moment, we don’t support the addition of comments or comment marker annotations using programmatic APIs. This is something that might change in future.

Deleting a Comment

You can delete an individual comment by clicking the delete button (delete icon). If all the comments of a thread are deleted, the corresponding root annotation is automatically deleted.


Comment editing isn’t supported in the current version.

Disabling the Comments UI

If your license includes comments but you want to disable letting the user view and add comments, you can set showComments to false in ViewState:

const initialViewState = new PSPDFKit.ViewState({
	showComments: false,

const instance = PSPDFKit.load({
	// ... other options
	initialViewState: initialViewState,

Comment Permissions

There might be situations where you want to disable the creation or deletion of individual comments based on some condition. To do this, you can define the isEditableComment function as a configuration option when initializing PSPDFKit. When the return value of the isEditableComment method is false for a comment, the comment can no longer be deleted by the user. Similarly, isEditableComment can be used to determine whether or not a user can reply to existing threads:

	// ...
	isEditableComment: (comment) => {
		return comment.rootId !== rootAnnotationId;

In the above example, all the comments that have a root annotation with an id other than rootAnnotationId will be editable.

For every comment thread, isEditableComment receives a temporary draft comment with pageIndex=null. The rootId of this draft comment points to the root annotation of the comment thread. If isEditableComment returns false, the user won’t be able to add comments in that comment thread:

	// ...
	isEditableComment: (comment) => {
		return comment.pageIndex !== null;

In the above example, a user can’t add a comment in any comment thread.

In case you want to set the permissions after a PSPDFKit instance has been created, you can use instance.setIsEditableComment:

PDPDFKit.load(options).then((instance) => {
	instance.setIsEditableComment((comment) => {
		return comment.rootId !== rootAnnotationId;

Customizing a Comment Block

You can customize the look of a comment block by using CSS. Please make sure you’re using the public class names starting with PSPDFKit-, as other class names might change in the future and break your application.

For example, if you want to customize the border-radius of avatars, you can do that by writing the following CSS:

.PSPDFKit-Comment-Avatar {
	border-radius: 6px;

You can also show avatars in comment blocks by setting a custom renderer:

	customRenderers: {
		CommentAvatar: (comment: Comment) => ({
			node: element,
			append: false, // This should always be `false` in this case.

If you want to change the avatar after the instance has been created, you can use setCustomRenderers.

Responsive UI

The UI adapts to the screen size of your browser. In the case of large screens, comment threads are displayed in a sidebar on the right-hand side of a document and are always visible, while on smaller screens, the threads are only visible after you tap on a root annotation.

Rich Text Comments

Rich text editing is supported in Instant Comments. Using the UI, you can select parts of an Instant comment and do the following:

  • Make parts of the comment bold, italic, or underlined.

  • Change the color and the background color of parts of the comment.

  • Add hyperlinks to the comment.