I understand that there is PDF Password parameter which can be set in administrator, for all PDF exports and email attachments.
In the similar lines wanted to know if there is way to set password field to other file formats like Excel,CSV and doc etc.
yes your understanding is correct, you can set a password for PDF exports but currently not for Excel, Word etc. I'm not sure if this option is available in the 3rd-party software we use to export to spreadsheets etc, however, I think it's a very good idea of yours so I will raise an enhancement request for it.
Thanks for the clarification, looking forward for the enhancement.