Introduction to PDF Bookmarks and PDF Outlines
PDF bookmarks and PDF outlines (also known as a table of contents or bookmarks panel) are both features in PDF documents that help users navigate and organize the content of a document, but they serve slightly different purposes and have different functionalities.
PDF bookmarks are interactive links within a PDF document that provide users with a convenient way to access specific sections or pages within the document. They’re displayed in a separate navigation pane on the left side of the PDF viewer.
PDF Outlines (Table of Contents)
PDF outlines are structured lists of links in a PDF document that provide a table of contents and allow users to navigate through the document’s sections. These links point to a bookmark located inside the PDF document. The PDF outline is also displayed in a separate navigation pane on the left side of the PDF viewer.
PDF Bookmarks vs. PDF Outlines
Bookmarks and outline elements aren’t different in the PDF specification, and in fact, Adobe treats them equally.
To provide a more flexible approach to both customers and users, PSPDFKit considers the outline as part of the document, i.e. a navigable, hierarchical view of the document contents. Bookmarks, on the other hand, are seen as information that’s laid on top of the document. They help the user, and they’re heavily context-dependent, without hierarchical order.
However, the bookmarking experience may vary for the end user when they carry the same document across platforms and different vendor software.
You can find out more about these differences in this blog post.