You can set the permissions for individual files and folders in the Plesk control panel. To change file permissions follow the steps given below.
Step 1: Login to the Plesk control panel.
Step 2: Under Websites & Domains Select File Manager.
Step 3: Click httpdocs from the left tree.
Step 4: Enable the check box near the file for which you going to change the file permission.
Step 5: When you mouse hover on the selected file, you will get a drop down arrow next to the file name. Click on the drop down and select Change Permissions.
Step 6: Under Groups or User names, select the user or group for which you wish to give the file permission.
Step 7: Under Permissions, you can allow or deny the required file permission for the selected users and click OK.