Hello,
The "Save to PDF Link" is not able to capture local changes made to a web page.
This should be solvable with our API (
https://pdfcrowd.com/api/html-to-pdf-api/):
1/ The "Convert to PDF" link on your web page would submit the information about the overlay (overlay url, transformation matrix,..) to your server side application.
2/ Your application would generate HTML (or a unique web page) with the overlay positioned according to the received information, pass it to our API, and return back the resulting PDF.