Shows how to create a PDF version from an uploaded image.

document_uploader.rb

# encoding: utf-8
require 'carrierwave/processing/mime_types'

class DocumentUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick
  include CarrierWave::MimeTypes

  storage :file
  process :set_content_type
  #
  # Versions
  #
  version :preview do
    process :convert => :jpg
    process :resize_to_fit => [310, 200]

    def full_filename (for_file = model.source.file)
      super.chomp(File.extname(super)) + '.jpg'
    end
  end

  version :pdf do
    process :convert_to_pdf
    def full_filename (for_file = model.source.file)
      super.chomp(File.extname(super)) + '.pdf'
    end
  end
end

minimagick.rb

module CarrierWave
  module MiniMagick
    def convert_to_pdf
        manipulate! do |img|
          img.format('pdf', 0) do |convert|
            convert << "-format"
            convert << "pdf"
          end
          img
        end
        # HACK-NOTE: force and override the content type. This is to guarantee to upload the PDF with the correct content type.
        file.content_type='application/pdf'
    end
  end
end