PDF 1.4 Password hash cracking

[Mem5]

https://hashcat.net/wiki/doku.php?id=fre...ese_hashes

--increment: enable incremental mode (see #1 above)
--increment-min 4: set the minimum length of the password candidates to 4 (in this case)
--increment-max 6: set the maximum length of the password candidates to 6 (in this case)

Builtin charset :
?a = ?l?u?d?s
?b = 0x00 - 0xff

You may not need ?b..