Upgrade to Asciidoctor PDF 2

This guide is written for anyone making the switch from an Asciidoctor PDF 1.x release to an Asciidoctor PDF 2.x release. Although Asciidoctor PDF 2 was carefully designed to make this transition a smooth one, it is still a major release, so there are changes that may impact you. You’ll also want to begin taking advantage of the new and improved functionality.

This page doesn’t call attention to all the changes in the Asciidoctor PDF 2 release line. Rather, it focuses on the changes at the transition from Asciidoctor PDF 1 to Asciidoctor PDF 2. To find a complete list of changes to Asciidoctor PDF, refer to the CHANGELOG.

Breaking changes and removals

The Asciidoctor PDF 2 major release gave us the opportunity to clean up and refine some of the behavior of this converter. As a result, breaking changes and removals are customary. This section summarizes that changes that may impact your content and configuration in order to help you make the transition.

Runtimes and dependencies

Support for Ruby < 2.7 and JRuby < 9.2 has been removed.
The converter now relies on Ruby’s built-in multibyte support for the uppercase, lowercase, and capitalize text transforms; no additional gems are required.
It’s no longer necessary to use an unreleased version of the prawn-table gem with Asciidoctor PDF. If you are, please remove that dependency from your Gemfile and allow Asciidoctor PDF to handle the dependency on the prawn-table gem.
safe_yaml gem has been removed; YAML.safe_load from the Ruby stdlib is used instead.

Theming system and built-in fonts

Support for the pdf-style and pdf-stylesdir attributes has been removed (deprecated since 1.5.0.beta.1). Use the pdf-theme and pdf-themesdir attributes instead to specify the location of a custom theme.
A custom theme no longer inherits from the base theme when the extends key is not specified. Instead, it starts with no keys set (plus base-font-size starting in 2.3.2) and relies on fallback values when needed by the converter. If you’re getting errors after upgrading, this could be the culprit. To make your theme portable across versions of Asciidoctor PDF, explicitly declare the theme you want your theme to extend using the extends key.
The basic running footer is now enabled when you use the base theme or extend the base theme. (Previously, the basic running footer was only enabled if you used or extended the default theme.)
The top-margin key on block and prose categories in theme has been removed; space between delimited blocks and lists is now controlled using bottom margins only.
The previously undocumented vertical-spacing key has been removed from the built-in themes.
The lead category keys in theme have been replaced with the built-in role named lead.
Support for the <color> tag in passthrough and theme content has been removed; use <font color="…"> instead; may affect themes that use pseudo-HTML in the value of the content key.
The previously deprecated “ascii” fonts have been removed; only the more complete “subset” fonts are now bundled with the gem.

Document attributes and options

The deprecated chapter-label document attribute has been renamed to the chapter-signifier attribute.
The untitled section option has been renamed to the notitle option
Most blocks are now breakable by default. You can apply the unbreakable option on a block to revert to the old behavior.

Require paths and APIs

The asciidoctor-pdf/converter and asciidoctor-pdf/version shim scripts have been removed; use asciidoctor/pdf/converter and asciidoctor/pdf/version instead.
The Pdf module alias in the API has been removed in favor of PDF.

Deprecations

The following features are deprecated with the release of Asciidoctor PDF 2 and will be removed in the next major release.

The blockquote category prefix is deprecated in the theme; use the quote prefix instead. See Quote Category Keys.
The key category prefix is deprecated in the theme; use the kbd prefix instead. See Keyboard Macro Category Keys.
The literal category prefix is deprecated in the theme; use the codespan prefix instead. See Codespan Category Keys.
The outline-list category prefix is deprecated in the theme; use the list prefix instead. See List Category Keys.
The Optimizer#generate_file method is deprecated; use Optimizer#optimize_file instead.
The built-in default-with-fallback-fonts and default-for-print-with-fallback-fonts theme names are deprecated in favor of default-with-font-fallbacks and default-for-print-with-font-fallbacks, respectively.

New and noteworthy

Paragraph roles and indent

You can define custom roles in your theme and apply them to specific paragraphs in your document. See Custom Roles to learn how to create a custom role and Use a custom role for how to assign a custom role to a paragraph. Applying custom roles to other blocks is not yet supported. However, you can learn how to enable this feature using an extended converter on the extended converter use cases page.

With the advent of roles being supported on paragraphs, the lead category in the theme has been dropped and replaced by a built-in role named lead. See Built-in roles for details.

To control the indent of inner paragraphs (instead of all paragraphs), you can set the new prose-text-indent-inner key in your theme. See Prose Category Keys for details.

Breakable and unbreakable blocks

The following blocks are now breakable by default, which includes automatic anchor and caption orphan prevention:

Admonitions
Block images
Code blocks (literal, listing, and source)
Examples
Open blocks
Quote blocks
Sidebars
Verses

Tables and sections are breakable by default, but do not provide automatic anchor and caption orphan prevention. For tables, that means the anchor and caption can be left on the current page if the table is advanced to the next page. For sections, that means the section’s title may be left on the current page if the first content block doesn’t fit. However, you can turn on orphan prevention for tables and sections by adding the (seemingly redundant) breakable option as a hint.

The unbreakable option can be applied to all delimited blocks (including admonitions and tables), but not sections. When the unbreakable option is applied to a block, the converter will advance the block and its caption and anchor to the next page if it detects that the block would break across pages and it can fit on a single page.

Notitle section option

The untitled option on sections has been renamed to notitle. With the name change, it’s also gained new capabilities. The notitle option hides a section title in the body of a document, but displays the title in the TOC and allows the anchor resulting from that title to still be referencable. It can also be used to add an entry to the TOC for a preamble, anonymous preface, and imported PDF pages. See Hide Section Titles for examples and more details.

Blocks and block captions

Blocks and block captions gained a lot of new theming capabilities in Asciidoctor PDF 2. Here are a few of the highlights:

Padding: The theme can now control the padding on a block using a 2-value array for ends and sides or 3-value array with implied left side value.
Border width: The border width of delimited blocks, admonitions, and block images can be customized per edge with the border-width key.
Border style: The border style of delimited blocks, admonitions, and block images can be changed with the border-style key. Border styles include dashed, dotted, double, and solid.
Line height: Wherever font properties are accepted in the theme, you can now control the line height of blocks using the line-height key.
Anchor positioning: The anchor location for blocks can be positioned relative to the content using the block-anchor-top theme key.
Caption text alignment: The text alignment of captions can now be controlled independent of the block alignment using the global caption-text-align theme key or per block category with <category>-caption-text-align. The image-caption-text-align and table-caption-text-align theme keys accept the value inherit in addition to the standard text alignment values. The value inherit resolves to the alignment of the block image or table.
Global caption text decoration: The text decoration style, color, and width can be applied to captions globally with the caption-text-decoration-style, caption-text-decoration-color, and caption-text-decoration-width theme keys. See Caption Category Keys for more information.
Caption background color: You can now specify a background color for captions globally using the caption-background-color theme key or per block category (<category>-caption-background-color). See Caption Category Keys for more information.
Caption max-width: A caption’s max-width value can be set to a percentage of the content by passing the percentage as an argument to fit-content function.
First line of abstract: The theme can control the font color of first line of abstract using abstract-first-line-font-color key.

Notable fixes for blocks

Asciidoctor PDF now uses smarter bottom margin logic that prevents extra space from being added below blocks, particularly when blocks are nested or used inside an AsciiDoc table cell.
Syntax highlighting isn’t applied to a source block if the specialchars substitution is disabled.
Borders, shading, and padding aren’t applied to collapsible blocks.
The callouts substitution can be removed on code blocks.

Tables

Border widths and styles: The table border width can be customized per edge with the border-width key. The border style can be specified per edge by assigning an array of styles to the border-style key. Border styles include dashed, dotted, and solid.
Grid widths and styles: The width of table grid lines can be specified for rows and columns with the grid-width key. The style of the grid lines can be specified for rows and columns with the grid-style key. Grid styles include dashed, dotted, and solid.
Maximum caption width: The maximum caption width for tables can be set to a percentage of the content by passing an argument to the fit-content function.
Caption end: The table-caption-side theme key has been renamed to table-caption-end.

Notable fixes for tables

Vertical center alignment is correctly applied to regular table cells.
The border bottom is correctly applied to a table row when frame and grid are none.
The font size of a literal table cells and nested blocks in AsciiDoc table cells is now scaled.
AsciiDoc table cells inherit the font properties from the table.
The content of an AsciiDoc table cell is prevented from overrunning the footer or subsequent pages.
The top and bottom padding is taken into account when computing the height of an AsciiDoc table cell.
An error message is logged if a table cell is truncated.
Instead of raising an error, the converter logs an error and skips the table if the content cannot fit within the designated width of a cell.

Callout lists and numbers

The theming language now has a callout-list category. The new theme keys let you customize the font properties, text alignment, and item spacing of callout lists. The callout-list category includes the margin-top-after-code key that can control the top margin of callout lists that immediately follow a code block.

Notable fixes for callouts

Callout numbers in a callout list stay with primary text when an item is advanced to the next page.
A sequence of two or more callouts separated by spaces in a code block are processed correctly.
The font family assigned to conums in the theme is applied to the callout numbers displayed in code blocks.

Images and icons

Caption end: You can now configure whether the caption for a block image is placed above or below the image using the caption-end theme key. See Block Image Category Keys for the list of available image-caption theme keys and their value types.
Text alignment roles: The text alignment roles, such as text-center, are now supported on block images.
Roles for inline images: Roles and inherited roles are now supported on inline images.
Image-based icons: Asciidoctor PDF 2 now supports image-based icons. They’re resolved from iconsdir and should have the icontype file extension.
Add a link to an icon: The link attribute can now be set on the icon macro.
Admonition icon image: An admonition icon image can now be remote, if allow-uri-read is set, or a data URI.

Notable fixes for images and icons

Warnings from background SVGs are now passed through to the logger.
SVGs are correctly scaled down when fit=scale-down is used.
The textual label on an admonition is displayed if the icon image fails to embed.

Links and inline formatting

Typographical quotation marks: You can now define single and double quotation marks, such as › and », using the quotes key in the theme. See Quotes Category Keys for details.
Hexadecimal characters: Character references that contain both uppercase and lowercase hexadecimal characters are now supported.
Background color and border offset on links: You can now control the background color and border offset (only for background) of links from the theme.

Notable links and inline formatting fixes

A closing quote preceded by a trailing ellipsis is kept together with the text enclosed in typographic quotes.
The font size for superscript and subscript is computed correctly when the parent element uses em and % units.
Hyphenation exceptions are respected when a word is adjacent to a non-word character.
The pre-wrap role on honored on a phrase.
The id attribute can now be set on the link macro.

Fonts, font styles, and text transforms

Small caps: The text-transform theme key now accepts the smallcaps value. When smallcaps is specified, the lowercase ASCII letters (a-z) are replaced with their small capital letter variants.
normal_italic: The new normal_italic value for the font-style key resets the font style to normal, then applies the italic variant of a font family.
Noto Sans: Noto Sans is now bundled with Asciidoctor PDF. It is used as a fallback font in the sans-with-fallback-font theme and can be declared in a custom theme.
Ceiling and floor characters: The left and right ceiling and floor characters (⌈, ⌉, ⌊, and ⌋)were added to the M+ fallback font.
Checkmark, numero, and y with diaeresis glyphs: The heavy checkmark glyph (✔) was added to the fallback font; the checkmark and heavy checkmark (✓ and ✔) were added to the monospaced font; the № and ÿ glyphs were added to the default and fallback fonts.

Covers and title page

Front and back cover images: The front and back cover images can now be defined in the theme and the target can be a data URI.
Deactivate title page: The title page can now be deactivated from the theme by assigning false to the title-page category key.

TOC and PDF outline

PDF outline title and levels: You can now deactivate the PDF outline by unsetting the outline document attribute (:!outline:) as well as customize its title with outline-title and the section level depth and expansion with outlinelevels. See PDF Outline for details.
Deactivate running content on TOC pages: The header or footer can be deactivated on TOC pages by assigning the noheader or nofooter options on the toc macro.
TOC dot leader: The theme can control the font size of the dot leader in the TOC.
TOC location: The TOC can now be placed following the preamble by assigning the preamble value to the :toc: document attribute. Also, the TOC is only displayed at the first location of a toc macro.
Extended converter: An extended converter can now override the get_entries_for_toc method to insert or filter TOC entries.

Notable fixes for the TOC

An image now renders at the end of a section title in the corresponding TOC entry.

Footnotes

Reset numbering: Footnote numbering is now reset in each chapter.
Footnote reference label: The xreftext of a chapter is now added to the label of a footnote reference that refers to a previous chapter.
Unresolved footnote color: The theme can configure the font color of an unresolved footnote using the unresolved role.

Notable fixes for footnotes

A missing footnote reference is shown in superscript.
Footnotes defined in an AsciiDoc table cell are now rendered with the footnotes at the end of an article or chapter.

Index

Index columns: The theme can now configure the number of index columns using the index-columns key.
Style of page numbers: The new index-pagenum-sequence-style document attribute controls the style of sequential page numbers in the index when media=screen.

Notable fixes for the index

The index section isn’t rendered if there are no index entries.
A blank line is no longer inserted in the index when a term is forced to break.
Prepress page margins are honored on subsequent pages in the index.
Space in front of a hidden index term is now collapsed.

Running content and page numbering

Select the page where running content starts: Specify the page on which the running content starts being displayed by assigning an integer to the start-at theme key on the running-content category. Running content can also start after the TOC, wherever the TOC is placed, by assigning the keyword after-toc to the start-at key.
Configure where integer page numbering starts: Specify the page on which the integer (1-based) page numbering begins using the start-at key on the page-numbering category. Integer page numbering can start at the front cover by assigning the keyword cover to the start-at key. Or, you can have the page numbering start after the TOC, wherever the TOC is placed, by assigning after-toc to the start-at key. Alternatively, the theme can specify an offset from the first body page where the page numbering should begin when an integer is assigned to start-at.
Margin and content margin: The margin and content margin of the running content per periphery (header or footer) and per side (recto or verso) can now be configured from the theme. The margins in running content can be specified using a 2-value array for ends and sides or 3-value array with implied left side value.
Part and chapter numbers: If the partnums attribute is set, the part-numeral attribute is automatically set in the running content. If the sectnums attribute is set, the chapter-numeral attribute is automatically set in the running content.
Select a background per layout: The page-layout attribute is now set in the running content. You can use this attribute to select a background per layout.

Notable fixes for running content and page numbering

The pdf-folio-placement setting is honored even when media=prepress.
Prepress page margins honor the value of pdf-folio-placement.

Theming system

Print-optimised themes: Asciidoctor PDF 2 introduces two new print-optimized themes, named default-for-print and default-for-print-with-fallback-font.
Extends hierarchy: Asciidoctor PDF only extends a theme in the extends hierarchy once unless the theme is modified with !important.
Power operator: The theming language now supports the power operator. It has the same precedence as multiply and divide.
Base theme changes: The top and bottom padding on quote and verse blocks has been reduced in the base theme. The base-border-color is now set and used as the default border color. The border colors have been removed in the base theme so all border colors can be controlled using the base-border-color key when extending the theme.
Default theme changes: The top and bottom padding on quote blocks is now uniform in the default theme.
Rouge theme: A Rouge theme can now be specified as a theme class or instance (API only).