Signer Authentication: SMS and PIN Methods

Signer authentication adds an extra layer of security by requiring signers to verify their identity before they can access and sign a document. Xodo Sign supports two authentication methods: SMS and PIN.

How to Enable Authentication for a Signer

1. On the New Document page, add a recipient by clicking Add Signer or CC. Or click Edit on an existing recipient row to open the edit form.
2. In the recipient form, locate the Authenticate Signer section and click Enable Authentication.
3. A Signer Authentication dialog appears. Select your preferred method: SMS Method (recommended) or PIN Method.
4. Follow the steps for your chosen method (see below).
5. Click Save Changes on the recipient form to confirm. The recipient row will now show Auth Enabled instead of Auth Disabled.

SMS Method (Recommended)

SMS authentication sends a one-time code to the signer's mobile phone. This provides the highest level of security. The signer must enter the code before they can view or sign the document.

To set up SMS authentication:

1. Select SMS Method (recommended) in the Signer Authentication dialog.
2. Enter the signer's mobile phone number, including the country code (e.g., +1 for the US).
3. Click Enable SMS Authentication.

What the signer experiences: After receiving the document email, the signer clicks the link. The document content is blurred and access is locked. They request a one-time code by text message (typically arrives within 5–10 seconds), enter the code to unlock the document, then proceed to sign.

PIN Method

PIN authentication requires the signer to enter a personal identification number (PIN) that you set. The PIN must be at least 4 digits long. You share the PIN with the signer through a separate channel — Xodo Sign does not send the PIN automatically.

To set up PIN authentication:

1. Select PIN Method in the Signer Authentication dialog.
2. Enter a PIN of at least 4 digits in the PIN field.
3. Click Enable PIN Authentication.
4. Share the PIN with the signer securely (for example, by phone or a separate email). Do not include the PIN in the document invitation email.

What the signer experiences: The signer opens the document link and is prompted to enter the PIN to unlock it. Once the correct PIN is entered, they can review and sign the document.

Editing or Removing Authentication

To update or remove authentication for a signer, click Edit on their recipient row. The Signer Authentication dialog opens with the current settings. You can change the phone number (for SMS), update the PIN, switch methods, or click Remove Authentication to disable it entirely.

SMS Credits and Supported Countries

SMS authentication is supported for 228 area codes across many countries worldwide. Every paid Xodo Sign subscription includes at least 10 SMS-authenticated signers per month. Free and trial accounts include 2 SMS credits per month. If you exceed your monthly quota, an overage fee of $0.25 per signer applies and is billed the following month.

Note: SMS authentication is not available for Template Links. To disable SMS overages, go to Business Settings > Signing Preferences > Disallow overage billing for Signer Authentication via SMS.