Verify XML/PDF submitted content



When a fillable form gets posted to a web server either as an EMAIL/PDF/XML/XDP, is there a way the server can verify its authenticity of the submitted content.

I dont want the situation where users are submitting altered content or malformed content.

I essentially want to do something like this and am wondering it is possible.

1. sign the PDF

2. all submitted content will contain a hash of the signature which I can then verify on server side to make sure it originated from the same fillable PDF form.