Gravity Forms allows you to export Form Entries to a CSV file. If PDF(s) have been configured on the form and are active, you will have the option to include the PDF URL as a column in your export under the Select Fields setting.
Towards the bottom of the available options for the Select Fields setting will be the available PDFs, recognised by the prefix "PDF:".
There are a number of security protocols in place to prevent unauthorised access to PDF documents. Before using this feature it's recommended you review the documentation detailing PDF security.
Signed PDF URLs are not available to be included in the Entry Export.