anchor.diff:  
   CAUTION: You must declare all four variants.
   If you're missing the font file for one of the variants, configure it to use the same font file as the normal variant.
  -
  -You can use the key that you assign to the font in the font catalog anywhere the `font-family` property is accepted in the theme file.
  -For example, to use the Roboto font for all headings (section titles and discrete headings), use:
  -
  -[source,yaml]
  -----
  -heading:
  -  font-family: Roboto
  -----
  -
  -When you execute Asciidoctor PDF, specify the directory where the fonts reside using the `pdf-fontsdir` attribute:
  -
  - $ asciidoctor-pdf -a pdf-theme=basic-theme.yml -a pdf-fontsdir=path/to/fonts document.adoc
  -
  -You can specify multiple directories by separating the paths with either a comma (`,`):
  -
  - $ asciidoctor-pdf -a pdf-theme=basic-theme.yml -a pdf-fontsdir=path/to/fonts,path/to/more-fonts document.adoc
  -
  -or a semi-colon (`;`) (which requires enclosing the combined value in double quotes to escape the delimiter from the shell):
  -
  - $ asciidoctor-pdf -a pdf-theme=basic-theme.yml -a pdf-fontsdir="path/to/fonts;path/to/more-fonts" document.adoc
  -
  -To include the location of the bundled fonts in the search, include the `GEM_FONTS_DIR` token in the list:
  -
  - $ asciidoctor-pdf -a pdf-theme=basic-theme.yml -a pdf-fontsdir="path/to/fonts;GEM_FONTS_DIR" document.adoc
  -
  -When running Asciidoctor PDF on the JVM (perhaps using AsciidoctorJ PDF), you can refer a directory inside of any JAR file on the classpath by prefixing the path with `uri:classloader:`:
  -
  - $ asciidoctorj -b pdf -a pdf-theme=basic-theme.yml -a pdf-fontsdir="uri:classloader:/path/to/fonts;GEM_FONTS_DIR" document.adoc
  -
  -TIP: When Asciidoctor PDF creates the PDF, it only embeds the glyphs from the font that are needed to render the characters present in the document.
  -Effectively, it subsets the font.
  -While that saves space taken up by the generated PDF, you may still be storing the full font in your source repository.
  -To minimize the size of the source font, you can use {url-fontforge}[FontForge] to subset the font ahead of time.
  -Subsetting a font means remove glyphs you don't plan to use.
  -Doing so is not a requirement, simply a personal preference.
   
   You can add any number of fonts to the catalog.
   Each font must be assigned a unique key, as shown here:
  
positive.code: * roboto-italic.ttf (_originally Roboto-Italic.ttf_)
  * roboto-bold.ttf (_originally Roboto-Bold.ttf_)
  * roboto-bold_italic.ttf (_originally Roboto-BoldItalic.ttf_)
  
  Next, declare the font under the `font-catalog` key at the top of your theme file, giving it a unique key (e.g., `Roboto`).
  
  
negative.code: The limited character set of WINANSI, or the bland look of the built-in fonts, may motivate you to load your own font.
  Custom fonts can enhance the look of your PDF theme substantially.
  
  IMPORTANT: In order for a third-party font to work properly with Prawn (and hence Asciidoctor PDF), several modifications are required.
  See <<Preparing a Custom Font>> to learn how to prepare your font for use with Asciidoctor PDF.
  
  ==== Selecting Your Font
  
  To start, find the TTF file collection for the font you want to use.
  A collection typically consists of four font styles:
  
  * normal
  * italic
  