Save As error

Hi there everyone, I am pretty new to LiveCycle, and I am creating a pretty simple form.

I just need a bit of help with my Save as Button.

My goal is to Save the filled form to an specific folder, and the name of the file should come from one the fields on the form.

I tried following the following tutorial without any luck:

https://acrobatusers.com/tutorials/how-save-pdf-acrobat-javascript

Everytime I add any commands, even a simple   app.execMenuItem("Save");  I get a "Submit Cancel" Error.

What am I doing wrong?

Thanks in advance.