Saving

doc.download() returns the whole PDF, with every change you made, as bytes:

const bytes = await doc.download();

You don’t need to save to keep a change: the server stores each change when the call returns. download() is for when you want the file itself. See What the server keeps.

Save in the browser#

Wrap the bytes in a Blob and let the browser download it:

const bytes = await doc.download();
 
const url = URL.createObjectURL(new Blob([bytes], { type: 'application/pdf' }));
const link = document.createElement('a');
link.href = url;
link.download = 'contract-signed.pdf';
link.click();
URL.revokeObjectURL(url);

To send the file to your server instead, put the same Blob in a FormData or pass the bytes to fetch() as the body.

Save in Node#

import { writeFile } from 'node:fs/promises';
 
await writeFile('out.pdf', await doc.download());

Incremental or rewrite#

mode chooses how the file is written:

const bytes = await doc.download({ mode: 'rewrite' });

Pick by what the file is for:

• Signed documents: incremental. A signature covers the bytes as they were signed. An incremental save leaves those bytes alone, so the signatures stay valid. A rewrite would break every one of them, so a signed document refuses it with ProtectedDocument.
• After a redaction, or after deleting something sensitive: rewrite. An incremental file still holds the version from before your changes, and PDF tools can recover it. Only a rewrite leaves the removed content out. See Redaction.
• The smallest file: rewrite. It also leaves out anything nothing refers to anymore.
• Everything else: incremental. It’s the default, it’s fast, and it never changes the parts of the file you didn’t touch.

What the server keeps#

The server stores the file as it was uploaded, and never changes it. Your changes are stored beside it, as they happen, and everyone who opens the document sees them.

download() puts the two together into one PDF. With 'incremental', that’s the uploaded file with your changes added at the end; with 'rewrite', a new file without the earlier version.

Because the uploaded file is always inside an incremental download, give doc.download only to people who may see the document as it was uploaded. Everyone else can view it without downloading it: see Permissions.

Permissions#

Downloading needs the doc.download permission. Without it, download() fails with Forbidden, so check before you show a download button:

if (doc.security.allows('doc.download')) {
  showDownloadButton();
}

Good to know#

An unchanged document#

When nothing changed since you opened the document, an incremental download returns the exact bytes you opened. The same holds when you changed something and then changed it back, such as an annotation added and deleted again. That keeps a signed document exactly as it was signed.

Password-protected files#

A file that had a password when you opened it still has it after you save, in both modes.

Cancelling a download#

download() returns a promise you can cancel with .abort(), like every call. See Errors & cancelling.