3rd Party Solutions for Uploading Files with Marketo Forms Embedded in Website

I have a client who wants to add the ability to upload a file as part of a Marketo form submit. I've seen that Uploadcare.com offers a 3rd party solution for this but it's designed for use with a form on a Marketo Landing Page. My client doesn't use Marketo Landing pages and is looking for a way to enable file uploads with Marketo forms embedded on their website. Any recommendations or suggestions?