With Payable Forms you can automatically collect shipping addresses at checkout if you enable the Collect Shipping Address setting, located in the Checkout Settings section of the sidebar. With this setting enabled, the customer's shipping address will be collected when they are entering their billing information. The customer's address will be stored in two places for your reference:
The transaction data for the order in your payment account - you'll find it in your PayPal, Square, or Stripe account.
In the spreadsheet connected to your form.
If you are using PayPal's Advanced Card Checkout (details) and enable the Collect Shipping Address setting, your checkout will default to PayPal's standard checkout.