Go to Settings > Document templates:
You will be able to create a new document by clicking Add document template. In the example below we already have 3 document types created for a Budget, Proposal, or Invoice PDF.
Clicking on Add document template will take you to the next screen where you can:
Add a name to the document
Select the document type (invoice, budget or proposal)
Change the design (standard, elegant)
Decide which subsidiary it is for (if you're using this addon)
Change the document language
Add a tax or second tax
Add a standard note
Add a standard footer