the input file is in an encrypted format, then the output file must be
the same format (decrypted). To decrypt such a file, specify the
encrypted file as @var{input}. The output will be the equivalent
-plaintext file. You will be prompted for the password (or use
-@option{-p}, documented below).
+plaintext file.
+
+The password for encrypted files can be specified a few different
+ways. If the password is known, use the @option{-p} option
+(documented below) or allow @command{pspp-convert} to prompt for it.
+If the password is unknown, use the @option{-a} and @option{-l}
+options to specify how to search for it, or @option{--password-list}
+to specify a file of passwords to try.
Use @code{-O @var{extension}} to override the inferred format or to
specify the format for unrecognized extensions.
Be aware that command-line options, including passwords, may be
visible to other users on multiuser systems.
+When used with @option{-a} (or @option{--password-alphabet}) and
+@option{-l} (or @option{--password-length}), this option specifies the
+starting point for the search. This can be used to restart a search
+that was interrupted.
+
+@item -a @var{alphabet}
+@item --password-alphabet=@var{alphabet}
+Specifies the alphabet of symbols over which to search for an
+encrypted file's password. @var{alphabet} may include individual
+characters and ranges delimited by @samp{-}. For example, @option{-a
+a-z} searches lowercase letters, @option{-a A-Z0-9} searches uppercase
+letters and digits, and @option{-a ' -~'} searches all printable ASCII
+characters.
+
+@item -l @var{max-length}
+@item --password-length=@var{max-length}
+Specifies the maximum length of the passwords to try.
+
+@item --password-list=@var{file}
+Specifies a file to read containing a list of passwords to try, one
+per line. If @var{file} is @file{-}, reads from stdin.
+
@item -h
@itemx --help
Prints a usage message on stdout and exits.