Within Teamwork Projects you can set privacy on files added to your project so only certain users can access them.
You can set privacy on files when first uploading them to your project, or by editing an existing file.
In the file upload modal, click the privacy dropdown to change the privacy settings:
By default, file privacy will be set to 'Everybody on project.'
You can also set privacy to a particular company or companies, some individuals in one company, or some individuals across different companies:
To change the privacy of an existing file, click the options dropdown to the right of the file in the Files list, and select 'Edit File Details' from the dropdown menu:
Note: Site administrators in the owner company will always be selected (gray), as their permissions override privacy by default and they will always be able to see the item.
For more information on files see: Uploading files in the files area