Having HR Staff group with Edit Access would be sufficient. Make sure to set access in the Document Class level. 

​@kumarmvnk Yes that's also correct. Additionally, If you do not want others to see the document in the system, you can use the RESTRICTED ACCESS flag. By setting that only the users with access will see that document record in the system. This can also be set on the document or document class level (document class management\document default values).

As ​@Mayura Wasantha suggested above if you set this access level for the Document class level, you don't need to manually adjust it every time you create a document using that class.

Yes I have  RESTRICTED ACCESS  ..however having two groups one for staff as EDIT access amd for users with No access. 

However the issue is Empoyee is able to see LineManager/Superior ’s employee file docs and also LineManager/Superior can see employee’s docs where the need is none other than HR Staff should be able to vieew the documents as rest all are managed by HR Staff offline with emails.   

scenario two - if possible would like to know if only empoyee can view their own documents with no document revision as a one off load. 

sharepoint to IFS load- is thre an easy way to load sharepoint files into IFS for employee file data.