bhttp + multer

client.js

var stream = require('stream');
var bhttp = require('bhttp');
var Promise = require('bluebird');

Promise.try(function() {
    return bhttp.get('http://www.pdf995.com/samples/pdf.pdf');
}).then(function(response) {
    var bufferStream = new stream.PassThrough();
    bufferStream.end(response.body);
    var data = {
        from: 'whatever',
        to: 'whatever',
        files: bhttp.wrapStream(bufferStream, {filename: 'bla.pdf'})
    };
    return bhttp.post('http://localhost:3000', data);
});

server.js

var express = require('express');
var multer = require('multer');
var app = express();

var storage = multer.memoryStorage();
var upload = multer({ storage: storage });

app.post('/', upload.any(), function(req, res, next) {
	console.log('got pdf', req.files);
	res.end('bye');
});

app.listen(3000)
console.log('listening');