Upload pdf and images using Arc

Hi,
I’m trying to use arc to upload to s3, but facing some issues in the road.
Here what happens, if I upload {jpg, png, etc…} I want arc to run some transform on it before saving.
However that’s not the case for a pdf file. Could someone give me some direction?
My goal is to put both validate in a single file

arc: 0.11.0
arc_ecto: 0.11.1
phoenix: 1.4.0

Here is the code:

defmodule Cidades.AnexoUploader do
  use Arc.Definition
  use Arc.Ecto.Definition

  @versions [:original, :thumb, :mini_thumb]
  @extension_whitelist ~w(.jpg .jpeg .gif .png .pdf)

  #def acl(:thumb, _), do: :public_read
  @acl :public_read

  def validate({file, _}) do
    file_extension = file.file_name |> Path.extname |> String.downcase
    Enum.member?(@extension_whitelist, file_extension)

    cond do
      not (~w(.pdf) |> Enum.member?(Path.extname(file.file_name))) -> transform(:thumb, {file})
      (~w(.pdf) |> Enum.member?(Path.extname(file.file_name))) -> {:ok}
    end

  end

  def transform(:thumb, {file, _scope}) do
    {:convert, "-strip -thumbnail x500^ -gravity center -extent x500 -format jpg", :jpg}
  end

  def transform(:mini_thumb, {file, _scope}) do
    {:convert, "-strip -thumbnail 200x200^ -gravity center -extent 200x200 -format jpg", :jpg}
  end

  def filename(version, {_file, _scope}) do
    #file_name = Path.basename(file.file_name, Path.extname(file.file_name))
    #"#{version}_#{:os.system_time}"
    #"#{scope.uuid}_#{version}_#{file_name}"
    "#{version}"
  end

  # Override the storage directory:
  def storage_dir(_version, {_file, scope}) do
    IO.inspect(scope)
    "uploads/#{scope.uuid}"
    #"#{String.downcase(scope.tipo)}/#{scope.mun.cnpj}/#{scope.uuid}"
  end

#  def __storage do
#    case Mix.env do
#      :dev  -> Arc.Storage.Local
#      :test -> Arc.Storage.Local
#      _     -> Arc.Storage.S3
#    end

  #delete all versions of an avatar
  #def remove(scope) do
  #  storage_dir(nil, {scope.avatar, scope}) |> File.rm_rf!
  #end

  # Provide a default URL if there hasn't been a file uploaded
  # def default_url(version, scope) do
  #   "/images/avatars/default_#{version}.png"
  # end

  # Specify custom headers for s3 objects
  # Available options are [:cache_control, :content_disposition,
  #    :content_encoding, :content_length, :content_type,
  #    :expect, :expires, :storage_class, :website_redirect_location]
  #
  # def s3_object_headers(_version, {file, _scope}) do
  #   [content_type: MIME.from_path(file.file_name)]
  # end
end

How can I solve this?
Newcomer to forum, sorry for any miss…
arc, arc_ecto