Encoding::UndefinedConversionError when trying to translate file

Summary: when trying to download translated file, raises an error:

reproduce steps:

#rails console
test-app(dev)> doc = Rails.root.join("storage", "files", "file_name.pdf")
=> "full/path/to/file.pdf"
...
test-app(dev)> doc_handle = DeepL.document.upload(doc, 'EN', 'UK')
=> 
#<DeepL::Resources::DocumentHandle:0x000079d53d473c68
...
test-app(dev)> DeepL.document.download(doc_handle, Rails.root.join("storage", "files", "translated.pdf"))

/home/user/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/irb-1.14.3/lib/irb.rb:1262:in 'full_message': "\xC8" from ASCII-8BIT to UTF-8 (Encoding::UndefinedConversionError)

Actual Result (AR): Raises an error.
Expected Result (ER): The file is downloaded successfully.

Rails 7.2.2
Ruby 3.4.1