This extension uses custom <meta> elements, for example:

<meta name="document-title" content="The document title"/>
<meta name="subject" content="The document subject"/>
<meta name="author" content="The author"/>
<meta name="keywords" content="Comma, separated, keywords, list"/>
…

<meta> with the following name values provide information that is stored in the document catalog in the PDF.

Figure 12. Document properties shown by Acrobat Reader