if file uploaded is pdf, then convert each page to a PNG, and store in new models.

image_uploader.rb

include CarrierWave::RMagick
  include Magick  
  
  storage :file

  version :thumb, :if => :pdf? do
    process :resize_to_fill => [400,500]
  end

  version :profile do
    # process :convert => 'png'
    process :resize_to_fit => [200,300]
  end

  protected

  def pdf?(new_file)
    new_file.content_type.include? 'pdf'
    converting(new_file)
  end

  def converting(new_file)
    i = 0
    manipulate! do |image|
      pdf = ImageList.new image.filename
      png = pdf[i]
      png.write("#{Rails.root}/public/uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}/p#{i+1}.png")
      @page = Page.create()
      @page.presentation_id = "#{model.id}"
      @page.image = "p#{i+1}.png"  #Need this image_url to be the same location as the original file uploaded (same folder)
      @page.save
      i = i + 1
      png
    end
  end

to make it store in the correct location, I think you have to write to carrier wave cache then run store! and it would store it properly. There are a few articles that I think might help.

https://github.com/jnicklas/carrierwave/wiki/How-to%3A-Detect-a-new-file-in-a-mounted-uploader

https://github.com/jnicklas/carrierwave/wiki/How-to%3A-create-a-thumbnail-with-both-color-and-grayscale-versions-in-one-image

also if you look at how the converts usually work, you have to yield the new object, but you have many. So you might have to look at the carrier wave code to see what the yield sets and you would have to loop through and create those yourself.

def blahblah
      manipulate! do |img|
        img.write(current_path)
        img = yield(img) if block_given?
        img
      end
    end

The issue is your not dealing with a single file after you turn a pdf into multiple files, so it is tricky. I wish I had more time to help but it has been tough finishing up some stuff...hope this helps a bit :(