Once you have gone over our knowledge base articles we recommend you to try out the PDF Editor and add your own custom templates.
Few tips to get you started with the process:
Think ahead, or even draw out on a piece of paper how would you like the template to look like. This keeps you away from experimenting with designs on the PDF Editor
Often use the "Preview" option in the PDF Editor to see if the changes reflect your intention
Consider the length of the text of the real data and leave space for longer parts of the text. For example, your item names may be much longer than the example item names you see in the editor.
Consider design for templates that extend over multiple pages - header and footer will be used on all pages.