Is it possible to have someone add a document to a document library and then hide it from everyones view except a certain person? Or would a different App be more useful for this?
Yes you can do this through Permission management. Remove everyone permission after uploading it. The farm administrator will be able to see it anyway.
You could also mimic this functionality with a drop-off library (part of the Content Organizer for all 2013 versions, including SharePoint Online) -- having it move all of the documents there somewhere else after they are uploaded. Then you could have whatever permissions you wanted on the destination libraries
If you love the Powershell. Then you create a new Permission level call add-only and assign this permission level to all user who you want add items.
Give other person(who can view the items) as full control/ edit or whatever you want to give them
You can create an add only permission level using the following PowerShell script.
$spweb=Get-SPWeb -Identity "<site url>"; $spRoleDefinition = New-Object Microsoft.SharePoint.SPRoleDefinition; $spRoleDefinition.Name = "Submit only"; $spRoleDefinition.Description = "Can submit/add forms/files/items into library or list but cannot view/edit them."; $spRoleDefinition.BasePermissions = "AddListItems, ViewPages, ViewFormPages, Open"; $spweb.RoleDefinitions.Add($spRoleDefinition); $spweb.Dispose();