Formspree currently doesn't support <input type="file">, but that doesn't mean you can't let your users upload images or documents when using a Formspree form.
Instead, you can integrate with an external file upload service. Uploadcare is one example. First create an account and a project on Uploadcare, then include their widget:
<!-- The best place for this one is your <HEAD> tag -->
<script>UPLOADCARE_PUBLIC_KEY = "demopublickey";</script>
<script src="https://ucarecdn.com/libs/widget/2.10.2/uploadcare.full.min.js" charset="utf-8"></script>
<!-- This is where the widget will be. Don't forget the name attribute! -->
<input type="hidden" role="uploadcare-uploader" name="my_file" />as per the documentation, you can use that <input> inside the Formspree form and receive the URL of the document in your email address.