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+= Postprocessor Extension Example
+:navtitle: Postprocessor
+
+Purpose::
+Insert copyright text in the footer.
+
+== CopyrightFooterPostprocessor
+
+```ruby
+class CopyrightFooterPostprocessor < Asciidoctor::Extensions::Postprocessor
+  def process document, output
+    content = (document.attr 'copyright') || 'Copyright Acme, Inc.'
+    if document.basebackend? 'html'
+      replacement = %(<div id="footer-text">\\1<br>\n#{content}\n</div>)
+      output = output.sub(/<div id="footer-text">(.*?)<\/div>/m, replacement)
+    elsif document.basebackend? 'docbook'
+      replacement = %(<simpara>#{content}</simpara>\n\\1)
+      output = output.sub(/(<\/(?:article|book)>)/, replacement)
+    end
+    output
+  end
+end
+```
+
+== Usage
+
+```
+Asciidoctor::Extensions.register do
+  postprocessor CopyrightFooterPostprocessor
+end
+
+Asciidoctor.convert_file 'sample-with-copyright-footer.adoc', :safe => :safe
+```