Hi everyone, I have a suitelet form created with "GET" method and in this form I using form.addButton to add "Print" button and I want to print it as PDF, please advice how can I do this solution ?

Your "Print" sounds like you are submitting the suitelet form data with some extras. I'd recommend you add a submit button and get used to what your POST data looks like. Your suitelet can then process the POST data into a PDF using the N/render module. The POST response can then contain the PDF and be rendered to the user.

Or you could add client script (that includes the function associated with the print button) to your SuiteLet that calls a server side SuiteLet that can process your request to generate and return the PDF for you to display.