In the context of PDF, an “outline” is better known as a “bookmark”. While “bookmark” is the more common term, this type of object is referred to in the PDF specification as an “outline”. While this can be confusing, the two terms denote the same thing.

While outlines/bookmarks have a range of uses, at its most basic, a PDF bookmark is a navigational aid similar to a physical bookmark. It is designed to stand out, sits outside the document content properties, and links to a specific location within the source document.

Due to their electronic nature, outlines/bookmarks can be more flexible than traditional physical bookmarks, however. In addition to linking to a specific location, a PDF bookmark allows the document creator to specify the destination view, which combines location, layout and zoom level. This allows PDF bookmarks to link to zoomed-in or zoomed-out views of specific images or diagrams.

Each bookmark is assigned one or more actions. While such actions can simply link to locations within the source document, they can also link to locations in other documents, launch web pages, submit forms, execute JavaScript or perform a range of other functions. Please see below for a selection of Knowledge Base articles about working with bookmarks.