nodejs knox put to s3 results in a 403

I'm trying to upload to an Amazon s3 bucket using knox in a nodejs project but can't get past a 403 error. I've ensured that the key,secret, and bucket are properly set. I could really use some help here from those with more experience.

My node code is as follows:

var upload_test = function(){

var client = knox.createClient(
    {
      key: config.aws.key
    , secret: config.aws.secret
    , bucket: config.aws.bucket
    }
);

fs.readFile('test.pdf', function(err,buf){
    var req = client.put('6530/test.pdf', {
        'Content-length': buf.length,
        'Content-Type': 'application/pdf'
    });
    req.on('response',function(res){
        if(res.statusCode === 200){
            console.log('Success!');
            req.on('data',function(chunk) {
                console.log(chunk);
            });
        }
        else {
            console.log("Error statusCode: " + res.statusCode);
            console.log("URL: " + req.url);
            req.on('data',function(chunk){
                console.log(chunk);
            });
        }
    });
});

}