Password protected pdf (how does client unlock their tax return)?

[CFP]

How does client "unlock" the password protected pdf version of their tax return, sent to them by email? (things we forget after the end of the "regular" tax season)

[kreinard · Accepted solution]

The default password is a combination of the last four digits of their ssn or ein, plus their five digit zip code. 

[CFP]

Password is: Last four digits of SSN, plus five digits of ZIP.