You can add Product Variations to your item via the Edit form of your product. This allows you to offer different versions of the same product, such as Basic and Pro, at varying prices.
To add variations Edit your product, toggle down the Software Version, Files, Variations, & License panel then uncheck No Thanks and click the Add Pricing Variant button.
You may then specify a name, price, and tagline for the variant, followed by specifying which Downloads should be offered in the variant.
Once you're ready to offer the variant(s) up for sale simply change the Variant Status to Published. If you ever need to remove a variant after-the-fact (i.e. after a purchase has been made), change the status to Disabled, such that no new purchases can be made but existing customers will still be able to download it.
Your customers may now choose which variant to purchase from the product page: