Editing PDF (section)

=== Metadata ===

PDF files can contain two types of metadata.<ref name="pdf-ref-1.7" /> The first is the Document Information Dictionary, a set of key/value fields such as author, title, subject, creation and update dates. This is optional and is referenced from an <code>Info</code> key in the trailer of the file. A small set of fields is defined and can be extended with additional text values if required. This method is deprecated in PDF 2.0.

In PDF 1.4, support was added for Metadata Streams, using the [[Extensible Metadata Platform]] (XMP) to add XML standards-based extensible metadata as used in other file formats. PDF 2.0 allows metadata to be attached to any object in the document, such as information about embedded illustrations, fonts, and images, as well as the whole document (attaching to the document catalog), using an extensible schema.

PDF documents can also contain display settings, including the page display layout and zoom level in a Viewer Preferences object. Adobe Reader uses these settings to override the user's default settings when opening the document.<ref>{{cite journal |url = http://www.adobepress.com/articles/article.asp?p=412914 |title=Getting Familiar with Adobe Reader &gt; Understanding Preferences|date=September 2, 2005|access-date=January 12, 2023 |journal=Adobe Press|publisher=Pearson|url-status=live|archive-url=https://web.archive.org/web/20121023144614/https://www.adobepress.com/articles/article.asp?p=412914|archive-date=October 23, 2012}}</ref> The free Adobe Reader cannot remove these settings.