Add link to documentation as PDF version

Author: Maxime Gréau

conf/_properties.adoc

@@ -17,3 +17,5 @@
 :link-git-repo-doc-style: {link-github-exoplatform}/doc-style
 :link-git-repo-gatein: {link-github-exoplatform}/gatein
 :link-git-repo-jcr: {link-github-exoplatform}/jcr
+// PDF file
+:link-exo-developer-guide-pdf: http://developer.exoplatform.org/exo-developer-guide.pdf

index.adoc

@@ -4,6 +4,10 @@ include::conf/_properties.adoc[]
 
 This website is centralizing all resources useful for eXo developers and contributors.
 
+[NOTE]
+icon:file-pdf-o[title="eXo Developer PDF Version"]
+{link-exo-developer-guide-pdf}[Download this documentation as PDF version]
+
 include::content/sources.adoc[leveloffset=+1]
 
 include::content/ide.adoc[leveloffset=+1]