How to add bookmarks and a table of contents to a PDF

Bookmarks and a contents page do different jobs

• Bookmarks, also called the outline, live in the reader's side panel. They're always one click away, however far into the document you are, and they can be nested so chapters open to show their sections.
• A contents page is part of the document itself. It's what people see when they print the file or read it on a device that hides the side panel, and in a PDF its lines can be links too.
• Long documents want both: Long documents usually benefit from both, and they should match, so readers never find a section in one that's missing from the other.

How headings are detected

• The easiest route: If your document came from a word processor and used heading styles, the easiest route is to export it again with bookmarks turned on.
• What the tool does instead: When that isn't possible, PDF Bookmarks and TOC reads the text of each page and picks out lines that are bigger or bolder than the body text, fairly short and not repeated on every page.
• How levels are decided: Numbered headings like 3 and 3.2 get their level from the numbers. Everything else is ranked by size.
• Scanned pages need OCR first: Scanned pages have no text at all, so run OCR PDF first, then add bookmarks to the searchable copy.

Cleaning up the list

Detection gives you a strong start, but it's worth a quick look.

• Remove what isn't a heading: Remove lines that aren't really headings, like a large quote, a table title or a figure caption.
• Add what was missed: Add anything that was missed, like an appendix title set in normal text.
• Check the levels: the list works like a staircase, where each bookmark can be at most one step deeper than the one above it.
• Move and nest: Use the arrow buttons to move bookmarks and to nest or un-nest them, and fix a page number if a heading sits at the very bottom of a page and the section really starts on the next.

Adding the contents page

• What the page looks like: Tick the option to add a contents page and give it a title. The page is inserted before your first page, with each bookmark listed, indented by level, followed by a dotted line and its page number. Every line links to its page.
• Numbers adjust automatically: Because the new page pushes the rest of the document back, all bookmark targets and contents page numbers are adjusted automatically.
• Titles in other scripts: The page uses a standard Latin font, so for titles in Arabic, Urdu or other scripts it isn't added. The bookmarks still work, since PDF readers show them in any language.

Page numbers after the change

• What the contents page shows: The contents page shows the position of each page in the file, which is also what PDF readers show in their page box.
• Printed numbers shift by one: If your pages already have printed numbers that started at 1 on the first page, those printed numbers are now one lower than the real position.
• Renumber if they should match: You can leave that, or add fresh numbers with Add Page Numbers so what's printed matches the contents.
• Do it last: Do this last, after all pages are in their final order.

Bookmarks for merged documents

• The problem with merged files: When you join several files with Merge PDF, readers lose track of where one document ends and the next begins.
• Add one bookmark per document: After merging, open the result in the bookmarks tool, choose an empty list, and add one bookmark for the first page of each original file, named after it.
• Nest the headings you care about under each one if the documents are long.
• Why it helps: A bundle for a court, a client or an application is much easier to check when every part is one click away.

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