Message API/docs/components/pdf/page-insert-blank

Page Insert Blank

Insert blank pages into the current PDF with page-insert-blank.

Overview

The `page-insert-blank` action creates new blank pages inside the current PDF. The host does not provide another file for this workflow.

Instead, the host tells the viewer where to insert the blank pages, how many to create, and what size they should be.

Required fields: `pageRange`, `count`, `width`, and `height`.
Use document pixel units for `width` and `height`.
This action is useful when operators need spacer pages, title sheets, or placeholders.

Example

Insert two blank pages at the selected location in the current PDF.

viewerWindow.postMessage({
  type: 'pageManipulation',
  payload: {
    requestId: 'blank-1',
    action: 'page-insert-blank',
    pageRange: [[3]],
    count: 2,
    width: 816,
    height: 1056
  }
}, '*');

Example

Complete HTML Example

Use this full standalone HTML document when you want a minimal host page for blank-page insertion.

html

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>PDF Page Insert Blank Demo</title>
  <style>
    body {
      margin: 0;
      font-family: Arial, sans-serif;
      background: #0b1220;
      color: #e5e7eb;
    }
    .app {
      display: grid;
      grid-template-columns: 320px 1fr;
      gap: 12px;
      min-height: 100vh;
      padding: 12px;
    }
    .panel {
      border: 1px solid #2f3b4f;
      border-radius: 12px;
      background: #111827;
      padding: 12px;
      display: grid;
      gap: 10px;
      align-content: start;
    }
    .stack {
      display: grid;
      gap: 8px;
    }
    .row {
      display: flex;
      gap: 8px;
      flex-wrap: wrap;
    }
    input, button, select {
      width: 100%;
      border: 1px solid #2f3b4f;
      border-radius: 8px;
      background: #0f172a;
      color: #e5e7eb;
      padding: 8px 10px;
      font: inherit;
      box-sizing: border-box;
    }
    button {
      width: auto;
      cursor: pointer;
    }
    .pages {
      display: grid;
      gap: 8px;
      max-height: 60vh;
      overflow: auto;
    }
    .page {
      border: 1px solid #2f3b4f;
      border-radius: 10px;
      background: #0d1728;
      padding: 8px;
      display: grid;
      gap: 8px;
    }
    .page.active {
      border-color: #22d3ee;
    }
    iframe {
      width: 100%;
      height: calc(100vh - 24px);
      border: 1px solid #2f3b4f;
      border-radius: 12px;
      background: #04101c;
    }
    img {
      max-width: 100%;
      height: auto;
      display: block;
      background: #fff;
      border-radius: 8px;
    }
    .meta {
      font-size: 12px;
      color: #9ca3af;
    }
  </style>
</head>
<body>
  <div class="app">
    <div class="panel">
      <div class="stack">
      <input id="viewerUrl" value="http://localhost:5173" />
      <input id="fileUrl" placeholder="Public PDF URL" />
      <div class="row">
        <button id="loadViewerBtn">Load Viewer</button>
        <button id="loadPdfBtn">Load PDF</button>
      </div>
      <input id="targetRangeInput" value="[[0]]" />
      <input id="countInput" value="1" />
      <div class="row">
        <input id="widthInput" value="816" />
        <input id="heightInput" value="1056" />
      </div>
      <button id="blankBtn">Insert Blank Pages</button>
      <div id="pages" class="pages"></div>
    </div>
    </div>
    <iframe id="viewerFrame" title="PDF Page Insert Blank Demo Viewer"></iframe>
  </div>
  <script>
const viewerFrame = document.getElementById('viewerFrame');
const viewerUrlInput = document.getElementById('viewerUrl');
const fileUrlInput = document.getElementById('fileUrl');
const pagesEl = document.getElementById('pages');
let latestPageList = null;

function post(type, payload) {
  viewerFrame.contentWindow.postMessage({ type, payload }, '*');
}

function loadViewer() {
  viewerFrame.src = viewerUrlInput.value.trim();
}

function loadPdf() {
  post('view', {
    fileUrl: fileUrlInput.value.trim(),
    displayName: 'Demo User',
    username: 'demo.user',
    email: 'demo@example.com'
  });
}

window.addEventListener('message', (event) => {
  if (event.source !== viewerFrame.contentWindow) return;
  const data = event.data;
  if (!data || typeof data !== 'object') return;
  if (data.type === 'pageList') {
    latestPageList = data.payload;
    renderPages(data.payload.pages);
  }
  onViewerMessage(data);
});

function renderPages(pages) {
  if (!pagesEl) return;
  pagesEl.innerHTML = '';
  pages.forEach((page) => {
    const item = document.createElement('div');
    item.className = page.isSelected ? 'page active' : 'page';
    const actions = pageActions(page);
    item.innerHTML = [
      page.thumbnailDataUrl
        ? '<img src="' + page.thumbnailDataUrl + '" width="' + (page.thumbnailWidth || 120) + '" height="' + (page.thumbnailHeight || 160) + '" />'
        : '<div class="meta">No thumbnail data</div>',
      '<div><strong>' + (page.label || ('Page ' + (page.index + 1))) + '</strong></div>',
      '<div class="meta">' + (page.title || 'Default') + '</div>',
      actions
    ].join('');
    wirePageActions(item, page);
    pagesEl.appendChild(item);
  });
}

document.getElementById('loadViewerBtn').addEventListener('click', loadViewer);
document.getElementById('loadPdfBtn').addEventListener('click', loadPdf);

document.getElementById('blankBtn').addEventListener('click', () => {
  const pageRange = parseRangeInput(document.getElementById('targetRangeInput').value);
  const count = Number(document.getElementById('countInput').value);
  const width = Number(document.getElementById('widthInput').value);
  const height = Number(document.getElementById('heightInput').value);
  post('pageManipulation', { requestId: 'blank-1', action: 'page-insert-blank', pageRange, count, width, height });
});
function pageActions() { return ''; }
function wirePageActions() {}
function onViewerMessage(data) {
  if (data.type === 'pageManipulationResult') console.log(data.payload);
}
  </script>
</body>
</html>

Complete HTML Example

Live Preview

Open the focused demo to test blank-page insertion live.

PDF Page Insert Blank Demo

Focused live demo for page-insert-blank.

Preview opens in a large modal for zoom-friendly review.