Try this code:
'Create an instance of ReportViewer
Dim viewer As New Microsoft.Reporting.WinForms.ReportViewer()
'Set local report
'NOTE: MyAppNamespace refers to the namespace for the app.
viewer.LocalReport.ReportEmbeddedResource = "MyAppNamespace.Report1.rdlc"
'Create Report Data Source
Dim rptDataSource As New Microsoft.Reporting.WinForms.ReportDataSource("Product", data)
viewer.LocalReport.DataSources.Add(rptDataSource)
'Export to PDF. Get binary content.
Dim pdfContent As Byte() = viewer.LocalReport.Render("PDF", Nothing, Nothing, Nothing, Nothing, Nothing, Nothing)
'Creatr PDF file on disk
Dim pdfPath As String = "C:\temp\report.pdf"
Dim pdfFile As New System.IO.FileStream(pdfPath, System.IO.FileMode.Create)
pdfFile.Write(pdfContent, 0, pdfContent.Length)
pdfFile.Close()