Come to think of it, I remember "signing" pdfs in adobe reader by clicking a form field that produced a signature similar to[1]:
John Smith
Digitally signed by
CN=John Smith
[...]
This would satisfy the "ceremony" requirement. According to adobe[2] it looks like you can do this with self signed certificates, so it's completely free as well. But this option is significantly less popular than hellosign/docusign. I guess the value-add for them is having a web interface, but I'm not convinced it's worth the $150/year (significantly more for "business" or "enterprise" plans) for a web interface that essentially signs pdfs with self-signed certificates.[1] https://helpx.adobe.com/content/dam/help/en/acrobat/11/using...
[2] https://helpx.adobe.com/acrobat/11/using/signing-pdfs.html#S...