Reducing header and footer height

I have a header quite far from the page top and this leads to quotes printing on two pages.
Is there a place where I can specify smaller margins to regain some page space for data?
Is this in some css file (where please ?)
Thanks
Stephane

All the code you need can be found in the templates folder, either edit the default or create your own.

Invoice templates are located:
application/views/invoice_templates/pdf/

The CSS files specified in the default invoice template are:
assets/THEME/css/templates.css
assets/core/css/custom-pdf.css