How to fix ("pdf" is not a class/module).

[Diego Bertaso]

Hello everybody.

How can I fix the error  ("pdf" is not a class/module) on rails 3.2.6 and ruby 2.3.8 when try generate a pdf from an application rails 3.2.6.

Prawn::Document.generate "assignment.pdf" do |pdf|

   pdf.font "Times-Roman"

   pdf.draw_text content, :at => [200,720], :size => 32

end

Thanks in advance.

Best regards.