index.js

var wkhtmltopdf = require('wkhtmltopdf');
var MemoryStream = require('memorystream');

process.env['PATH'] = process.env['PATH'] + ':' + process.env['LAMBDA_TASK_ROOT'];

exports.handler = function(event, context, callback) {
    var body = JSON.parse(event.body);
	var memStream = new MemoryStream();
    var content;
	if (body.htmlBase64 != null) {
        content = new Buffer(body.htmlBase64, 'base64').toString('utf8');
    } else {
	    content = body.url;
    }
	wkhtmltopdf(content, body.options, function(code, signal) {
	    const response = {
            statusCode: 200,
            body: JSON.stringify({
                pdfBase64: memStream.read().toString('base64'),
                options: body.options
            })
        };
        callback(null, response);
	}).pipe(memStream);
};