Unable to get PDF hash?

[17und4]

Hi guys,

I´m trying to get a Hash from an encrypted PDF document and I´m trying to use the recommended (hashcat wiki) tool: pdf2hashcat.py

It worked for some files before but now I have one pdf document where I get this error message:

Code:

content.pdf : Can't find trailer

Hmm ... any idea what could have caused this message and how I can resolve this?

Thanks a lot in advance!