Cracking pdf file with arabic password using hashcat
If you cannot get things to work with the application you can try and use the source code instead. A lot of these tools are open source. Then you can specify the character set directly and/or use an Arabic dictionary.

The password itself is not stored when a password is hashed. That means that the precise encoding details are lost - the password hashing algorithms themselves process bytes, not characters usually. Nowadays a lot of password hashes and applications default to UTF-8 though, which can encode any character set. UTF-16 and UTF-16LE can also be tried, with and without BOM header.

However, to find out which character set is used just from the hash (instead of, say, a protocol specification) you can only try.