How to create a sign pdf web application like ilovepdf sign-pdf using PDF-LIB?

I have a Laravel website. I need a pdf viewer that can also add handwritten signatures.

I found PDF-LIB as a pdf editor. But the website only explains how to edit using hard code.

I need a user interface for the editor, for example the website https://www.ilovepdf.com/sign-pdf. But I have no idea how to make it.

So, how do I make it?