No, there is no need to have translated papers of any kind into Greek language.
However recently the Hellenic Coastguard here in Kalamata (Messinian Bay) fined a German motorboat owner for his papers.
He has had only papers to use his boat in german inland waters (rivers and chanels) but not at coastal waters or even at sea.
We others first thought the fine was because his papers are not greek language. After some investigation we found out that he has no licenses to drive at sea.
Amel Sharki #60
Currently Kalamata, Greece