New staff

IS have the ability to grant users with rights to the entire document libraries and that is the process that should be used when a new member of staff comes on board.  IS should be notified that this is a requirement and they will action appropriately.

Existing staff

You can grant a group or individual access to a single file or a folder. 

Navigate to the SharePoint site. Find the file or folder you want to share. Click the tick next to the file or folder.  Click Share from the top navigation.  You will see a pop-up box.
Search for the person you want to share with and click their name.  Click the pencil icon and choose whether to grant them edit or read rights.  Add a message if you wish.  Click Send. The user will then receive an email with a link saying they have been allowed access.