Rails + Prawn: undefined method `table' for #<Prawn::Document:0x007fda2d594a98>:

You should add these lines into your Gemfile.

gem 'prawn', '~> 1.2.1'
gem 'prawn-table', '~> 0.1.0'

The line in the documentation is WRONG. add require 'prawn/table' to your .pdf.prawn file on the top and it will work.