Replace the 'Add to Cart' button with a 'Pre-Order' button
Palo Alto uses product tags for creating Pre-order products. When you define a Pre-order tag, you can easily convert the 'Add to Cart' button to a 'Pre-Order' button.
Setting up a Pre-order tag is very simple and can be done right in your Shopify Admin.
To remove the Buy it now button, you can create a Pre-order product template and uncheck 'Show dynamic checkout buttons' under the Form block.