def to_file( file = suggested_filename )
            execute do | contents |
                if file.is_a?(String)
                    FileUtils.mv contents, file
                else
                    file.write contents.read
                    file.rewind
                end
            end
            file
        end
def to_file( file = suggested_filename )
            execute do | contents |
                if file.is_a?(String)
                    FileUtils.mv contents, file
                else
                    file.write contents.read
                    file.rewind
                end
            end
            file
        end
Save the PDF to the file
 @param file [String,IO] if file is a String, the PDF is moved to the path indicated (most efficient).
        Otherwise, file is considered an instance of IO, and write is called on it with the PDF contents
 @return [String,IO] the file