Problem

The Save Document Library as Template option is not available on the default Documents library that gets created by the site publishing feature.

Cause

This is a known issue in SP 2010 and a work-around has been provided.

Work-around

Open the document library -> Library Settings

On your address bar, change the link from this:

https://sharepointsite/_layouts/listedit.aspx?List=%7BAE8E37D9%2DCC63%2D4324%2D9A78%2D97D2E5426252%7D

to this:

https://sharepointsite/_layouts/savetmpl.aspx?List=%7BAE8E37D9%2DCC63%2D4324%2D9A78%2D97D2E5426252%7D

You should now be able to save your document library as a template.