How can I add a warning to #printpage
when its disabled if its chosen saying please check required fields?
You can use JS function checkValidity(), this will return false if the form is not valid.
https://developer.mozilla.org/en-US/docs/Web/API/HTMLSelectElement/checkValidity
isValid = $('.form').checkValidity()
if (!isValid) {
$('#printpage').innerText = "Please fill in required fields";
} else {
$('#printpage').innerText = "";
}
Your html should contain HTML validity checkers, such as required.
<input required type="text" class="thisIsAClass" />