Automatic XML generation as an attachment in the PDF

Many thanks @Thom Parker. After reading through what you shared, I'm still unsure. I use the code below in the button to generate the submission form (basically to check if all fields completed) :

var emptyFields = [];

for (var i = 0; i < this.numFields; i++) {
var f = this.getField(this.getNthFieldName(i));

var aPages = (typeof(f.page) == "object") ? f.page : [f.page];
aPages = aPages.filter(a => a > -1 && a < 9);

if (f.type !== "button" && f.required && aPages.length && f.required) {
if (f.valueAsString === f.defaultValue) {
emptyFields.push(f.name);
}
}
}

if (emptyFields.length > 0) {
app.alert("Please complete the following fields:\n" + emptyFields.join("\n"));
} else {
app.execMenuItem("SaveAs");
}

To generate the PDF file for submission, I thought it would be possible to attach a copy of the form in a "*.xfdf" embedded automatically in the PDF