Flatten PDF forms using Javascript

Annotation or form flattening refers to the operation that changes annotations (such as markup, widgets, 3D models, etc.) into a static area that is part of the PDF document, just like the other text and images in the document.

Forms share a relationship with annotations because the visual display of a form is a widget annotation. The process of flattening annotations therefore can optionally flatten forms as well. By flattening and merging existing annotation appearances with page content, the original annotations are deleted from the PDF pages.

Note that it is not possible to undo the flatten operation. An alternative approach to annotation or form flattening is to set the annotation to ReadOnly. The ReadOnly property on the Annotation class enables this modification. If it's read only then it can't be edited or deleted.

To flatten annotations, you can perform this when getting the PDF file data or while downloading the PDF file locally. There is also the option to flatten select annotations .

Use the getFileData method and the flatten option for the annotations to be flattened in the document output when getting the data for uploading to a server.

WebViewer({
  fullAPI: true,
  // other constructor options
}

// config.js
const { documentViewer, annotationManager } = instance.Core;

document.getElementById('myBtn').addEventListener('click', async () => {
  const doc = documentViewer.getDocument();
  const xfdfString = await annotationManager.exportAnnotations();
  const options = { xfdfString, flatten: true };
  const data = await doc.getFileData(options);
  const arr = new Uint8Array(data);
  const blob = new Blob([arr], { type: 'application/pdf' });
  // upload blob to your server
});

Use the downloadPdf method and the flatten option for the annotations to be flattened in the document output when downloading the PDF locally.

WebViewer({
  fullAPI: true,
  // other constructor options
}

// config.js
document.getElementById('myBtn').addEventListener('click', () => {
  // download pdf with all annotations flattened
  instance.UI.downloadPdf({
    includeAnnotations: true,
    flatten: true,
  });
});

Use flattenAnnotations method to flatten all annotations into a document.

WebViewer({
  fullAPI: true,
  // other constructor options
}

// config.js
const { documentViewer, PDFNet, annotationManager } = instance.Core;

document.getElementById('myBtn').addEventListener('click', async () => {
  await PDFNet.initialize();
  const doc = await documentViewer.getDocument().getPDFDoc();

  // export annotations from the document
  const annots = await annotationManager.exportAnnotations();

  // Run PDFNet methods with memory management
  await PDFNet.runWithCleanup(async () => {

    // lock the document before a write operation
    // runWithCleanup will auto unlock when complete
    doc.lock(); 

    // import annotations to PDFNet
    const fdf_doc = await PDFNet.FDFDoc.createFromXFDF(annots);
    await doc.fdfUpdate(fdf_doc);

    // flatten all annotations in the document
    await doc.flattenAnnotations();

    // or optionally only flatten forms
    // await doc.flattenAnnotations(true);

    // clear the original annotations
    annotationManager.deleteAnnotations(annotationManager.getAnnotationsList());

    // optionally only clear widget annotations if forms were only flattened
    // const widgetAnnots = annots.filter(a => a instanceof Annotations.WidgetAnnotation);
    // annotationManager.deleteAnnotations(widgetAnnots);
  });

  // clear the cache (rendered) data with the newly updated document
  documentViewer.refreshAll();

  // Update viewer to render with the new document
  documentViewer.updateView();

  // Refresh searchable and selectable text data with the new document
  documentViewer.getDocument().refreshTextData();
});

Use the flatten method on annotation objects to flatten select annotations into the document.

WebViewer({
  fullAPI: true,
  // other constructor options
}

// config.js
const { documentViewer, PDFNet, annotManager } = instance.Core;

document.getElementById('myBtn').addEventListener('click', async () => {
  await PDFNet.initialize();
  const doc = await documentViewer.getDocument().getPDFDoc();

  // export annotations from the document
  const annots = await annotManager.exportAnnotations();

  // Run PDFNet methods with memory management
  await PDFNet.runWithCleanup(async () => {

    // lock the document before a write operation
    // runWithCleanup will auto unlock when complete
    doc.lock();

    // import annotations to PDFNet
    const fdf_doc = await PDFNet.FDFDoc.createFromXFDF(annots);
    await doc.fdfUpdate(fdf_doc);

    const page = await doc.getPage(1);
    const annotation = await page.getAnnot(0);
    await annotation.flatten(page); //flatten this annotation

    // clear the original annotations
    annotManager.deleteAnnotations(annotManager.getAnnotationsList());

    // import annotations from PDFNet
    const fdfDoc = await doc.fdfExtract(PDFNet.PDFDoc.ExtractFlag.e_both);
    const xfdf = await fdfDoc.saveAsXFDFAsString();
    annotManager.importAnnotations(xfdf);
  });

  // clear the cache (rendered) data with the newly updated document
  documentViewer.refreshAll();

  // Update viewer to render with the new document
  documentViewer.updateView();

  // Refresh searchable and selectable text data with the new document
  documentViewer.getDocument().refreshTextData();
});