This script will modify how the title page, part-title, and chapter-title are rendered.

custom_page_layout.rb

require 'asciidoctor-pdf'

class CustomPdfConverter < Asciidoctor::PDF::Converter
  register_for 'pdf'

  # Customize the title page layout
  def layout_title_page(doc)
    start_new_page
    font 'Helvetica', size: 48, style: :bold
    text doc.doctitle, align: :center, valign: :center
    move_down 30
    font 'Helvetica', size: 20
    text doc.attr('author', 'Anonymous'), align: :center
    move_down 10
    text doc.attr('revdate', Time.now.strftime('%Y-%m-%d')), align: :center
    move_down 20
    text "Custom Title Page", align: :center
  end

  # Customize the part-title layout
  def layout_part_title(part)
    start_new_page
    font 'Helvetica', size: 36, style: :bold
    text part.title, align: :center, valign: :center
    move_down 50
    font 'Helvetica', size: 24
    text "Part #{part.number}", align: :center
    start_new_page
  end

  # Customize the chapter-title layout
  def layout_chapter_title(chapter, opts = {})
    # Start new chapter page
    start_new_page unless at_page_top?
    move_down 200 if chapter.number == 1 # Add top padding for the first chapter
    
    # Set the custom title for the chapter
    font 'Helvetica', size: 32, style: :bold
    text chapter.title, align: :center

    # Optional: Customize chapter number display
    move_down 20
    font 'Helvetica', size: 18, style: :italic
    text "Chapter #{chapter.number}", align: :center

    # Start new page after title if necessary
    start_new_page
  end
end

custom_page_layout_ASCIIDoctor.md

Once you have saved the script: custom_page_layout.rb , you can pass it to the asciidoctor-pdf command to generate the PDF with custom page layouts.

Run the following command:

asciidoctor-pdf -r ./custom_page_layout.rb my_document.adoc