How it works

A headless viewer is a few parts that always work the same way. Learn them once here, and every plugin page reads the same: the same kind of service, the same kinds of settings and events, the same checks.

The viewer and its documents#

provideEmbedPdf() sets up the engine, the plugins and the open documents. Put it in a component’s providers, and that component and everything in its template can use them:

viewer.ts

import { Component } from '@angular/core';
import { EpdfDocumentGate, provideEmbedPdf } from '@embedpdf/angular/runtime';
import { EpdfRenderLayer, withRender } from '@embedpdf/angular/render';
import { EpdfPageTemplate, EpdfStage, withStage } from '@embedpdf/angular/stage';
import { engine, source } from './pdf';
import { Toolbar } from './toolbar';

@Component({
  selector: 'app-viewer',
  imports: [Toolbar, EpdfDocumentGate, EpdfStage, EpdfPageTemplate, EpdfRenderLayer],
  providers: [
    provideEmbedPdf({ engine, initialDocuments: [{ source }] }, withStage(), withRender()),
  ],
  template: `
    <app-toolbar />
    <epdf-stage *epdfDocumentGate="let document; fallback: opening">
      <ng-template epdfPage>
        <epdf-render-layer />
      </ng-template>
    </epdf-stage>

    <ng-template #opening><p>Opening…</p></ng-template>
  `,
})
export class ViewerPage {}

It works the same in your app config or in a route’s providers. engine is a function that creates the engine: it runs only in the browser, and it may return a promise, so a dynamic import() keeps the engine out of the page’s first download. A document that comes from an input or a route parameter goes on the Stage instead, <epdf-stage [document]="source()">: when the source changes, the new document opens and the old one closes.

A viewer can have several documents open, like tabs, and one of them is active. A component talks to the active document unless it’s inside an element with [epdfDocumentScope]: then every service it injects acts on that document. That’s how a tab strip or a side-by-side view gives each part its own document:

document-scope.ts

import { Component, input } from '@angular/core';
import { EpdfDocumentScope } from '@embedpdf/angular/runtime';
import { EpdfRenderLayer } from '@embedpdf/angular/render';
import { EpdfPageTemplate, EpdfStage } from '@embedpdf/angular/stage';

@Component({
  selector: 'app-document-pane',
  imports: [EpdfDocumentScope, EpdfStage, EpdfPageTemplate, EpdfRenderLayer],
  template: `
    <div [epdfDocumentScope]="documentId()">
      <epdf-stage>
        <ng-template epdfPage>
          <epdf-render-layer />
        </ng-template>
      </epdf-stage>
    </div>
  `,
})
export class DocumentPane {
  readonly documentId = input.required<string>();
}

*epdfDocumentGate renders the element it’s on only once the document is open, so the components inside can count on it. See Opening documents.

Plugins#

A plugin adds one feature. You register it in provideEmbedPdf(), with its settings:

plugins.ts

import type { ApplicationConfig } from '@angular/core';
import { provideEmbedPdf } from '@embedpdf/angular/runtime';
import { withRender } from '@embedpdf/angular/render';
import { withSearch } from '@embedpdf/angular/search';
import { withStage } from '@embedpdf/angular/stage';
import { engine } from './pdf';

export const appConfig: ApplicationConfig = {
  providers: [
    provideEmbedPdf({ engine }, withStage({ layout: 'horizontal' }), withRender(), withSearch()),
  ],
};

Most plugins keep their state per document: each open document has its own search, its own selection, its own zoom. A few belong to the whole viewer, such as translations, commands and stamp libraries.

What a plugin gives you#

Every plugin gives your components one service, inject(EpdfSearch) for search, with four parts:

Part	Gives you	For search
Methods	the plugin’s API: everything it can do	`search.search({ text })`, `search.nextHit()`
Signals	the data to show, such as the number of hits	`search.hitCount()`
Streams	a call to your function when something happens	`search.completed$`
Settings	the plugin’s current settings, as a signal	`search.settings()`

Search is the example; every plugin follows the pattern: inject(EpdfAnnotation), inject(EpdfSelection), and so on. A plugin without settings has no settings(), and one without events has no streams. The Stage follows it too, with inject(EpdfStageRef): inside a Stage it’s that Stage, and anywhere else the main Stage of the document in scope. From around a Stage, a template reference, <epdf-stage #stage="epdfStage">, or viewChild(EpdfStage) reaches it.

search-box.ts

import { Component, inject } from '@angular/core';
import { EpdfSearch } from '@embedpdf/angular/search';

@Component({
  selector: 'app-search-box',
  template: `
    <input #query (input)="search.search({ text: query.value })" />
    <span>{{ search.activeHitIndex() + 1 }} of {{ search.hitCount() }}</span>
    <button (click)="search.nextHit()">Next</button>
  `,
})
export class SearchBox {
  protected readonly search = inject(EpdfSearch);
}

Do things with its methods. The service is the same object for as long as your component lives, so call it from event bindings, effect() or your own methods.
Show things with its signals. Read them in your template or in a computed(). A signal updates only what reads it, so a count doesn’t redraw a list.
React to things with its streams. They’re RxJS observables, and takeUntilDestroyed() stops listening when your component goes away:

match-announcer.ts

import { LiveAnnouncer } from '@angular/cdk/a11y';
import { Component, inject } from '@angular/core';
import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
import { EpdfSearch } from '@embedpdf/angular/search';

@Component({
  selector: 'app-match-announcer',
  template: '',
})
export class MatchAnnouncer {
  private readonly announcer = inject(LiveAnnouncer);
  private readonly search = inject(EpdfSearch);

  constructor() {
    this.search.completed$
      .pipe(takeUntilDestroyed())
      .subscribe(({ hitCount }) => this.announcer.announce(`${hitCount} matches`));
  }
}

All four together: the API searches, the state shows the count, the event announces each finished search, and the settings change the highlight color.

Loading live preview…

import {
  ChangeDetectionStrategy,
  Component,
  effect,
  inject,
  signal,
  ViewEncapsulation,
} from '@angular/core';
import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
import { EpdfDocumentGate, provideEmbedPdf } from '@embedpdf/angular/runtime';
import type { OpenInput } from '@embedpdf/angular/runtime';
import { EpdfPageTemplate, EpdfStage, withStage } from '@embedpdf/angular/stage';
import { EpdfRenderLayer, withRender } from '@embedpdf/angular/render';
import { EpdfSearch, EpdfSearchLayer, withSearch } from '@embedpdf/angular/search';
import { localEngine } from '@embedpdf/engine';

const ebook = async (): Promise<OpenInput> => {
  const response = await fetch('https://snippet.embedpdf.com/ebook.pdf');
  return { kind: 'bytes', bytes: new Uint8Array(await response.arrayBuffer()) };
};

const colors = ['#ffd500', '#7dd3fc', '#86efac'];

@Component({
  selector: 'demo-search-box',
  changeDetection: ChangeDetectionStrategy.OnPush,
  template: `
    <div class="toolbar">
      <input
        #field
        class="field"
        type="search"
        aria-label="Search"
        [value]="text()"
        (input)="text.set(field.value)"
      />
      <!-- The data to show: signals, which update only what reads them. -->
      <output class="readout">
        @if (search.hitCount() > 0) {
          {{ search.activeHitIndex() + 1 }} of {{ search.hitCount() }}
        } @else {
          No matches
        }
      </output>
      <!-- The API: what search can do. -->
      <button type="button" class="button" (click)="search.nextHit()">Next</button>
      <!-- The settings: a signal too, so the pressed swatch follows the highlight color. -->
      @for (swatch of colors; track swatch) {
        <button
          type="button"
          class="swatch"
          [attr.aria-label]="'Highlight in ' + swatch"
          [attr.aria-pressed]="search.settings().highlight.color === swatch"
          [style.background]="swatch"
          (click)="search.updateSettings({ highlight: { color: swatch } })"
        ></button>
      }
      <button type="button" class="button" (click)="search.resetSettings()">Reset</button>
    </div>
    <p class="announcement" aria-live="polite">{{ announcement() }}</p>
  `,
})
export class SearchBox {
  // One service for everything: the API, the data, the events and the settings.
  protected readonly search = inject(EpdfSearch);
  protected readonly colors = colors;
  protected readonly text = signal('PDF');
  protected readonly announcement = signal('');

  constructor() {
    // A call to your function when something happens: an RxJS stream.
    this.search.completed$
      .pipe(takeUntilDestroyed())
      .subscribe(({ hitCount }) =>
        this.announcement.set(`The search finished with ${hitCount} matches.`),
      );

    effect(() => {
      const text = this.text();
      void this.search.search({ text });
    });
  }
}

@Component({
  selector: 'demo-root',
  imports: [
    EpdfDocumentGate,
    EpdfStage,
    EpdfPageTemplate,
    EpdfRenderLayer,
    EpdfSearchLayer,
    SearchBox,
  ],
  providers: [
    provideEmbedPdf(
      { engine: () => localEngine(), initialDocuments: [{ source: ebook }] },
      withStage(),
      withRender(),
      withSearch(),
    ),
  ],
  changeDetection: ChangeDetectionStrategy.OnPush,
  styleUrl: './hooks.css',
  encapsulation: ViewEncapsulation.None,
  template: `
    <ng-container *epdfDocumentGate="let document; fallback: loading">
      <demo-search-box />
      <epdf-stage class="stage">
        <ng-template epdfPage>
          <epdf-render-layer />
          <epdf-search-layer />
        </ng-template>
      </epdf-stage>
    </ng-container>

    <ng-template #loading><p class="loading">Opening…</p></ng-template>
  `,
})
export class App {}

A few signals read one specific thing, and the ones that need an argument are methods that return a signal: annotation.watch(filter), document.pages() or shell.surface(id).

Layers and overlays#

What you draw goes in one of two places.

Layers draw inside each page. The Stage stamps out its <ng-template epdfPage> once per visible page, and each layer draws for that page. Later layers sit on top:

layers.ts

import { Component } from '@angular/core';
import { EpdfAnnotationLayer } from '@embedpdf/angular/annotation';
import { EpdfRenderLayer } from '@embedpdf/angular/render';
import { EpdfSearchLayer } from '@embedpdf/angular/search';
import { EpdfSelectionLayer } from '@embedpdf/angular/selection';
import { EpdfPageTemplate, EpdfStage } from '@embedpdf/angular/stage';

@Component({
  selector: 'app-pages',
  imports: [
    EpdfStage,
    EpdfPageTemplate,
    EpdfRenderLayer,
    EpdfSearchLayer,
    EpdfSelectionLayer,
    EpdfAnnotationLayer,
  ],
  template: `
    <epdf-stage>
      <ng-template epdfPage>
        <epdf-render-layer />
        <epdf-search-layer />
        <epdf-selection-layer />
        <epdf-annotation-layer />
      </ng-template>
    </epdf-stage>
  `,
})
export class Pages {}

A layer zooms, scrolls and rotates with its page, and you never convert a position: everything a plugin gives you is in page coordinates, and the layer places it. A page’s layers also keep out of each other’s way: while an annotation layer or a form layer is on the page, the render layer leaves what it draws out of the page picture, so nothing is drawn twice.

Overlays float above the pages, attached to something on them: a menu next to the selected text, a card next to an annotation. They go inside <epdf-stage>, next to the page template, which keeps them attached while the user scrolls and zooms. See Menus over the page.

Loading live preview…

import {
  ChangeDetectionStrategy,
  Component,
  effect,
  inject,
  signal,
  ViewEncapsulation,
} from '@angular/core';
import { EpdfDocument, EpdfDocumentGate, provideEmbedPdf } from '@embedpdf/angular/runtime';
import type { OpenInput } from '@embedpdf/angular/runtime';
import { EpdfPageTemplate, EpdfStage, withStage } from '@embedpdf/angular/stage';
import { EpdfRenderLayer, withRender } from '@embedpdf/angular/render';
import { withInteraction } from '@embedpdf/angular/interaction';
import { EpdfSearch, EpdfSearchLayer, withSearch } from '@embedpdf/angular/search';
import {
  EpdfSelection,
  EpdfSelectionLayer,
  EpdfSelectionMenu,
  withSelection,
} from '@embedpdf/angular/selection';
import { localEngine } from '@embedpdf/engine';

const ebook = async (): Promise<OpenInput> => {
  const response = await fetch('https://snippet.embedpdf.com/ebook.pdf');
  return { kind: 'bytes', bytes: new Uint8Array(await response.arrayBuffer()) };
};

@Component({
  selector: 'demo-root',
  imports: [
    EpdfDocumentGate,
    EpdfStage,
    EpdfPageTemplate,
    EpdfRenderLayer,
    EpdfSearchLayer,
    EpdfSelectionLayer,
    EpdfSelectionMenu,
  ],
  providers: [
    provideEmbedPdf(
      { engine: () => localEngine(), initialDocuments: [{ source: ebook }] },
      withStage(),
      withRender(),
      withInteraction(),
      withSelection(),
      withSearch(),
    ),
  ],
  changeDetection: ChangeDetectionStrategy.OnPush,
  styleUrl: './layers.css',
  encapsulation: ViewEncapsulation.None,
  template: `
    <ng-container *epdfDocumentGate="let document; fallback: loading">
      <div class="toolbar">
        <label class="option">
          <input
            #search
            type="checkbox"
            [checked]="showSearch()"
            (change)="showSearch.set(search.checked)"
          />
          Search matches
        </label>
        <label class="option">
          <input
            #selection
            type="checkbox"
            [checked]="showSelection()"
            (change)="showSelection.set(selection.checked)"
          />
          Text selection
        </label>
      </div>
      <!-- Layers draw inside each page, later ones on top; the menu floats above them. -->
      <epdf-stage class="stage">
        <ng-template epdfPage>
          <epdf-render-layer />
          @if (showSearch()) {
            <epdf-search-layer />
          }
          @if (showSelection()) {
            <epdf-selection-layer />
          }
        </ng-template>
        @if (showSelection()) {
          <epdf-selection-menu>
            <div class="menu">
              <button type="button" (click)="clearSelection()">Clear the selection</button>
            </div>
          </epdf-selection-menu>
        }
      </epdf-stage>
    </ng-container>

    <ng-template #loading><p class="loading">Opening…</p></ng-template>
  `,
})
export class App {
  protected readonly showSearch = signal(true);
  protected readonly showSelection = signal(true);
  private readonly search = inject(EpdfSearch);
  private readonly selection = inject(EpdfSelection);
  private readonly document = inject(EpdfDocument);

  constructor() {
    // Something on every layer on load: the matches of a search, and the title selected.
    effect(() => {
      const cover = this.document.pages()[0]?.ref;
      if (!cover) return;
      void this.search.search({ text: 'PDF' });
      this.selection.select({ page: cover, start: 10, count: 52 });
    });
  }

  protected clearSelection() {
    this.selection.clear();
  }
}

Settings#

A plugin’s settings are the options you pass when you register it, and each plugin page lists them under Settings. Every plugin lets you change them while the app runs, for example when the user picks another layout:

stage.updateSettings({ layout: 'grid' });
stage.resetSettings(); // back to what you registered

Every plugin with settings has the same three calls, a settings() signal, and a settingsChanged$ stream.

Colors are settings too, such as the highlight of a search match or the handles of an annotation. Each color setting can also come from a CSS variable, which wins over the setting, for dark mode or a different look per viewer: see Colors & theming.

Checks before you act#

Anything the user may not be allowed to do has a check with the same name: annotation.canCreate(), search.canSearch(), pageEdit.canEdit(). Use them to hide or disable buttons. The engine checks every call again, so they keep your UI honest; they’re not the guard. See Permissions.

Good to know#

Code outside components#

Code that isn’t a component, such as a keyboard handler, analytics or a test, uses the same services: inject them in a service of your own, provided next to provideEmbedPdf().

outside-components.ts

import { Injectable, inject } from '@angular/core';
import { EpdfSearch } from '@embedpdf/angular/search';

/** Provide it next to the viewer: `providers: [provideEmbedPdf(…), SearchShortcuts]`. */
@Injectable()
export class SearchShortcuts {
  private readonly search = inject(EpdfSearch);

  handleKey(event: KeyboardEvent) {
    if (event.key === 'F3') this.search.nextHit();
  }
}

With provideEmbedPdf() in your app config, every service in the app can inject them. In a test, replace one the Angular way: { provide: EpdfSearch, useValue: fakeSearch }.

Plugins don’t touch the page#

Plugins hold state and logic, never HTML. The framework packages draw. That’s why every plugin works the same in React, Vue, Svelte and Angular, and why you can use a plugin’s API in a test without a browser.

Coordinates#

Every position is in points from the top-left corner of the page, with y going down. Layers and overlays convert to pixels for you. See Coordinates.

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