Removed "Add Row" button post sign

Hello!

I will preface this first as I am very much a novice at coding. I'm taking some classes, but it's very much a work in progress for me. 🙂

I have an Adobe form that has buttons on it that will allow the user to add a row if they need to add more information. For example, if there is more than one evaluator on a performance evaluation. Right now, the form is set up to only be visible on the screen, meaning that the buttons will disappear when it prints. So we are having to "print as pdf" to save a copy that does not have the buttons. 

I was wondering if there is a way to make the buttons disappear once the form is signed? Everyone has to use electronic signatures to sign. I used the "postSign" function, but when I test it I get the following error:

I feel like I'm probably missing a step, or that there is a better way to do it. 

Thanks!