PDF 1.4 Password hash cracking

[rico]

Your command doesn't really matter. The GTX 970 benchmarks at about 7800 kH/s for this hash type so even just 8 character passwords including all characters is 95^8 combinations. It will take almost 30 years to try all 8 char combinations on the 970.

9 chars will take two and a half millennia...

Maybe a nice dictionary attack might be better (unless passwords are randomly generated).