Can not access Sharepoint documents on Mobile Sharepoint app when access rights is set to view

The users are not able to access Sharepoint PDF documents on Mobile Sharepoint app when access rights is set to view. On trying out couple of different access rights we realized the minimum access right required is read. The problem of giving access with read will allow users to download the documents which is to be restricted. Any ideas on how to set access rights to avoid download but at the same time allow users to only view documents.