Docutain allows you to create document types that can be assigned to your documents.
How these are created or changed is explained here:
1. Create a document type via main menu
Select "Document type" from the main menu or tap in the Document type field while creating a document.
Tap on the "plus" symbol at the bottom right to create a new document type.
Then assign a name for your new document type and confirm by tapping on "Save".
Your new document type is now available.
2. Change a document type
Select "Document type" from the main menu.
Then tap on the "pencil icon" behind the document type you want to change.
Change the document type as desired and confirm by tapping on "Save".