If you are sending signatureRequest url via email, you can protect document content with OTP. OTP can be sent via:
- E-mail – openOtpEmail
- SMS – openOtpPhone (signature Request package with SMS addon is requested)
OTP is sent to the email or telephone number after opening the signatureRequest and pressing button “Send verification code”.

{
"rules": "openOtpEmail-email@adress.com",
"filedata": {
"content": "xyz_JVBERi0xLjc==",
}
}