The Cloud Adapter is a stateless, synchronous service that receives messages from the on-premise instance of SQL Server. This service is required when you are deploying a database from your on-premise SQL Server instance to a SQL Server deployed on an Azure Virtual Machine.

Cloud Adapter is supported with SQL Server 2012 and higher. On SQL Server 2012, the Cloud Adapter for SQL Server requires SQL Management Objects.

For your SQL Server 2012 installation, you will need the SQL Server Cloud Adapter to be installed. This is available for download from the SQL Server 2014 Feature Pack. The filename that you need to download is SqlCloudAdapter.msi.

When you try to install this on your Azure VM, you might end up with the error message below:

Service cannot be started. System.IO.FileNotFoundException: Could not load file or assembly ‘Microsoft.SqlServer.SqlEnum, Version=12.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91’ or one of its dependencies. The system cannot find the file specified.
File name: ‘Microsoft.SqlServer.SqlEnum, Version=12.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91′
   at Microsoft.SqlServer.Management.CloudAdapter.Service.CloudAdapterService.ReadConfigurationParameters()
   at Microsoft.SqlServer.Management.CloudAdapter.Service.CloudAdapterService.OnStart(String[] args)
   at System.ServiceProcess.ServiceBase.ServiceQueuedMainCallback(Object state)

The above error message clearly states that the version number that the installer is looking for is SQL Server 2014 i.e. version = 12.0.0.0. You can install this assembly when Microsoft® SQL Server® 2014 Shared Management Objects (SharedManagementObjects.msi) is installed from SQL Server 2014 Feature Pack.

Reference:
Cloud Adapter for SQL Server
http://msdn.microsoft.com/en-us/library/dn169301.aspx