node.js sendgrid how to attach a pdf

Im using sendgrid to send email in my node.js application. Every combination I try to attach a pdf ends up with my attached pdf being unreadable.

i've tried:

fs.readFile('public_html/img/Report.pdf',function(err,data){
        var base64data = new Buffer(data).toString('base64');

        sendgrid.send({
            to        : hexDecode(_.e),
            from      : 'xxxxxxxxx@gmail.com',
            subject   : 'Report',

            files     : [{filename:'Report.pdf',content:'data:application/pdf;base64,'+base64data}],
            //files   : [{filename:'Report.pdf',contentType:'data:application/pdf',url:'public_html/img/'Report.pdf'}],
            //files   : [{filename:'Report.pdf',url:'public_html/img/'Report.pdf'}],
            html      : 'bla bla'

does any one know how to prevent 'Failed to load pdf document'??