The reason this service is free is to show you what you can do with re:PDF. All you need in order to collect data over the internet is a PDF form! The server does the rest including a submit button in your form, a database, e-mail notifications, reports (Excel, XML and HTML) and so on. Publishing your form for data capturing requires 3 clicks and 20 seconds of your time.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.