I am looking into how to implement pdf signing with certificates for a side project I am trying to turn into a business (think signing an offer letter). can any

I am looking into how to implement pdf signing with certificates for a side project I am trying to turn into a business (think signing an offer letter). can anyone point me to some good resources for learning more? I have only a basic understanding of cryptography. or if you'd be willing to chat sometime id really appreciate it.