Unfortunately, Airtable’s extensions cannot be automated in any way.
If you'd like to automate the process of creating a PDF document and inserting the PDF file into an Airtable attachment field, you would need to turn to external document creation apps.
Here are some of your best options:
1. DocuMint: One of the most popular and fully-featured PDF creation tools for Airtable is DocuMint. This is the gold standard for creating PDF files from Airtable.
Alternatively to page designer, you can use typeflow.us for generating pdf based on Airtable data. We offer a lifetime plan currently at 150$. This plan lets you generate as many pdf as needed.