The header appears at the top of the page of a document and the footer, at the end. Now, you can choose to set header/footer on every page of the document or front page only.

Go to Settings-> Templates and click on template Name to open the template (Invoice/Quote/Purchase Order/Report) that you want to modify.

There is a checkbox “Show on every page” under 'Upload Your Logo' and also under 'Bottom Logo' section. Tick the box if you want to show the header and/or footer on every page or leave it unchecked if you want it to appear only on front page.

Click on 'Save' button to save the template.