In case you need to remove the SharePoint Library ribbon option of "Upload Document" to a library:

...and have the following scenario presented to the user:

1. Open the library in SharePoint designer
2. Open the "All Documents" view (in our case)
3. Find the ending tag for <asp:Content ContentPlaceHolderId="PlaceHolderMain" runat="server">
4. Just before </asp:Content> insert the following CSS as shown below:

</ZoneTemplate></WebPartPages:WebPartZone>

<style type="text/css">
/*
hide the New Document, Upload Document, New Folder on left side of ribbon, have to use the back slashes to escape the dots in the element ID
*/
#Ribbon\.Documents\.New {display:none;}
</style>

</asp:Content>