saveAsPdf.ps1

function saveAsPdf($filename) {
    echo ("Converting {0}" -f $filename)
    $excel = New-Object -ComObject Excel.Application -Property @{visible=$false}
    try {
        $excel.AlertBeforeOverwriting = $true
        $workbook = $excel.Workbooks.Open($filename)
        $workbook.ExportAsFixedFormat(
            [Microsoft.Office.Interop.Excel.XlFixedFormatType]::xlTypePDF ,
            [Io.Path]::ChangeExtension($filename, '.pdf') , 
            [Microsoft.Office.Interop.Excel.XlFixedFormatQuality]::xlQualityStandard
        )
    } finally {
        $excel.Quit()
    }
}

echo $("Begin to convert {0} files to PDF" -f $args.Length)
$args | %{ saveAsPdf -filename $_ }
echo "DONE"