There isn't a way to make the "Name your Job" setting for products required. (This setting is found in Sites > [site name] > Products > [product name] > General tab in the "CheckOut Options for This Product." It is labeled "Allow Edit of Product Name on Ordering.")
However, you could use the identifying field in eDocBuilder. This setting is found on the Template Info tab of the template. Once you set an identifying field, the contents of that field will automatically be used in the name of the production file. For example, you could set the name field on your template as the identifying field. In this way, you aren't relying on the user to enter anything, and the system adds the name to the name of the production file automatically. Please note that the identifying field has to be a user-provided text field. Also, please note that If you turn on an identifying field in eDoc AND allow the customer to name their job, the identifying field will override whatever the customer types in the name their job area on the product page.