Add example to generate pdf document in FDP

PR:             253178
Submitted by:   kib@

documentation/content/en/books/fdp-primer/doc-build/chapter.adoc

@@ -48,7 +48,10 @@ Different types of output can be produced from a single AsciiDoc source file.
 |Electronic Publication. ePub file format.
 |===
 
-To render the documentation and the website use one of the following examples.
+[[doc-build-rendering-html]]
+=== Rendering to html
+
+To render the documentation and the website to `html` use one of the following examples.
 
 [[documentation-build-example]]
 .Build the documentation
@@ -83,6 +86,23 @@ To render the documentation and the website use one of the following examples.
 ....
 ====
 
+[[doc-build-rendering-pdf]]
+=== Rendering to pdf
+
+To generate a document in `pdf` format use this command.
+In this example the English Handbook will be used.
+In order to export the document correctly all the extensions should be passed used the `-r` argument.
+
+[[document-pdf-example]]
+.Build the entire documentation project
+[example]
+====
+[source,bash]
+....
+asciidoctor-pdf -r ./shared/lib/man-macro.rb -r ./shared/lib/git-macro.rb -r ./shared/lib/packages-macro.rb -r ./shared/lib/inter-document-references-macro.rb -r ./shared/lib/sectnumoffset-treeprocessor.rb --doctype=book -a skip-front-matter -a pdf-theme=./themes/default-pdf-theme.yml content/en/books/handbook/book.adoc
+....
+====
+
 [[doc-build-toolset]]
 == The FreeBSD Documentation Build Toolset