To explain, let's consider Purchase Order which has the following fields in the Print Format, and here, I want to add Supplier's Contact Name under Supplier Name and remove the Weight Per Unit column from the Item's table.
Navigate to the Print View of the document you want to change the Print Format of -> Menu (...) -> Customize
Search for the field by name and add it to the desired location
Follow the same drag and drop method to remove the fields as well.
To add/remove the fields from the child table of the document: Locate the table -> Select Columns -> Check/Uncheck as you wish.