In the page designer block, when I click save as PDF the document has a header generated by Airtable (with the date and time) and footer (with some http:…)
I don’t think that’s coming from Airtable. If you’re printing (i.e. saving a print as a PDF) from your web browser, that info is generated by the browser. There should be an option in the print dialog settings (or possibly the browser settings) to turn it off.