I am using org-mode to generate html pages from my notes. I used Publishing Org-mode files to HTML to setup blog system.

I have defined an export template. But to use it I have to add following line in top of my every org file inside my notes project.

#+SETUPFILE: ~/.emacs.d/org-templates/level-0.org

Is there a way to set this up in .emacs or to customize an org-mode variable so that I do not have to place this line in every file?

According to org-mode manual, #+SETUPFILE is an in-buffer setting. Does this mean I cannot define it globally for all org files?

These two answers on SU tell how to customize style for HTML export. But my template file contains other settings besides CSS style. So only customizing style won't do it for me.