how to get edited fields from the pdf

[jwd24]

Hi all, Javascript/HTML newbie here.

I have a PDF file with editable fields that I can load into an iframe using the PDFLib.PDFDocument.load and getElementByID javascript commands as shown here:
const url = './MyPDF.pdf'
const existingPdfBytes = await fetch(url).then(res => res.arrayBuffer())
const pdfDoc = await PDFLib.PDFDocument.load(existingPdfBytes)
const pdfDataUri = await pdfDoc.saveAsBase64({ dataUri: true });
document.getElementById('pdf').src = pdfDataUri;

I can then edit the fields in this iframe/PDF in my browser, but I don't know how to read back this updated PDF.
If I use the getFields() command on pdfDoc, I just get back my original data, not what I manually updated.
Is there a way to get this manually updated data?

Note that I tried using the contentWindow command to read the contents of the iframe and then turn that into a pdfdoc via the load command, but that didn't work. It fails with a 'No PDF header found' error. I guess frameContent is not an object that can be used
by load().
var frameObj = document.getElementById('pdf');
var frameContent = frameObj.contentWindow.document.body.innerHTML;
const pdfDoc2 = await PDFLib.PDFDocument.load(frameContent)

Thanks,
John

[AYGTX]

bumping this

[jwd24]

Since submitting my original question about how to read edited fields from a pdf, I’ve discovered the "Adobe Embed API" which provides this capability.
With that API, I’m able to present a ‘save’ button on my webpage containing the pdf such that when clicked, it sends the updated pdf to me via a callback function.