def compile(options = {})

            load_all_objects unless loaded?

            #
            # A valid document must have at least one page.
            #
            append_page if pages.empty?

            #
            # Allocates object numbers and creates references.
            # Invokes object finalization methods.
            #
            physicalize(options)

            #
            # Sets the PDF version header.
            #
            version, level = version_required
            @header.major_version = version[0,1].to_i
            @header.minor_version = version[2,1].to_i

            set_extension_level(version, level) if level > 0

            self
        end
def compile(options = {})

            load_all_objects unless loaded?

            #
            # A valid document must have at least one page.
            #
            append_page if pages.empty?

            #
            # Allocates object numbers and creates references.
            # Invokes object finalization methods.
            #
            physicalize(options)

            #
            # Sets the PDF version header.
            #
            version, level = version_required
            @header.major_version = version[0,1].to_i
            @header.minor_version = version[2,1].to_i

            set_extension_level(version, level) if level > 0

            self
        end
This method is meant to recompute, verify and correct main PDF structures, in order to output a proper file.
 * Allocates objects references.
 * Sets some objects missing required values.