To explain how, we have written a step by step tutorial to take you through the process of adding price information to your documents.
The tutorial guides you on how to create template overrides for your document edit forms and detail views. You will learn how to work with the parameters property of each document to store and retrieve your custom information.
When finished, you will have all of the know-how to save and display whatever information you want about your documents, without messing with the database.
Happy Coding!