How to give user authentication

[kzala7]

want to provide login credentials when someone wants to access some documents

[kranthi]

Create the user and add the user to respective site with consumer permissions then they can access the documents in read only mode.

or 

If they access the documents for read-only mode then its better to share link to user where user no need to login.

Go through below links related to permissions/roles:

User roles and permissions | Alfresco Documentation  

Permissions / Roles | Alfresco Documentation 

[kzala7]

thank you kkumar