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I can find no reference to the device in question even having the option
It may be that it does not at all relate to the pdf format and is in fact the scan to email itself that requires a login from Xerox Standard Accounting.
To test this, go into email and change the format to tiff, if you still need a code it is Xerox Standard Accounting and the person who administers that needs to resolve it.
If there is a custom firmware for the machine , the option will be here in CWIS > Properties > Services > Email > Defaults > Filing Options
That area would look like this in the case there are indeed pdf passwords (Screenshot from another device that does have pdf passwords for email)