We need to create a storage location for a userguide(in any format pdf,excel etc) in salesforce and for that we have to give read only permissions to all users and Editable access to admin and selected users.

We have tried these two ways but couldn't find exact solution:

1- We have tried it using by creating a Folder in documents and giving readable access to all users and to give editable access to admin or some selected users we have created a permission set in which under System Permissions we just ticked the Manage public Documents checkbox.So by this all the users which are assigned in the permission set are able to manage all the folders but we want to manage only a particular folder.

2- We have also tried using content libraries.In that we created a library and added the content file in it.Gave permissions of viewing,editing to particular users but in this we are not able to add Chatter Only users so this solutions got breaked,adding to it some more profiles are asked to generate a case to salesforce support to get Salesforce CRM Content User License by this license only they can view or edit content.

Solutions for this is highly appreciable.And if any one can suggest how to modify any of above two ways to get required solution this will be a great help. I have also posted this question on salesforce community and Stack Exchage.

Thanks