Brother MFC 9970CDW - Manual (Page 193)

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 Settings tab
Choose the Target Application, File Type, Resolution, Scan Type, Document Size,
Duplex (two-sided) Scanning (For MFC-9560CDW and MFC-9970CDW, if necessary),
Show Scanner Interface, Brightness and Contrast settings.
If you choose Secure PDF from the File Type list, the Set PDF Password dialog box appears. Enter your
password in the Password and Re-type Password box and then click OK.
Note
Secure PDF is also available for Scan to E-mail and Scan to File.