PDF Bookmarks vs Table of Contents: What's the Difference?

A PDF bookmark is a title plus a destination. The destination is a page and, optionally, a position and zoom on that page. A bookmark can run an action instead, such as opening a web address. The full list of bookmarks is called the document outline, and the file's document catalog points to it.

Bookmarks nest. A chapter bookmark can hold section bookmarks, which can hold their own, and the reader shows them as a tree that folds open and shut. A PDF can also ask to open with the bookmarks panel already showing, through a setting called the page mode.

Bookmarks are not drawn on any page. They don't print, they don't change the page count and they never move page content.

Preview's Tools > Add Bookmark command marks a page for you while you read, and Apple lists those marks under View > Bookmarks. They are separate from the document outline that Preview shows under View > Table of Contents. To give every reader the same navigation, write the bookmarks into the PDF's outline with a bookmark editor.

A table of contents is ordinary page content. Its titles, dot leaders and page numbers are text drawn on one or more pages, usually right after the cover. It prints, it shows in page thumbnails and it counts toward the page total.

Text on a page is not clickable by itself. A contents row becomes a link only when a link annotation sits over it and points to a page. A link annotation is an invisible clickable rectangle. An automatic table of contents in Word is made of links, and saving as PDF from Word usually keeps them. A contents page typed by hand or scanned from paper has no links at all.

The page numbers on it are fixed text. If pages are added or removed later, the printed numbers stay the same and can send readers to the wrong page.

Bookmarks help a reader move around a file on screen. A table of contents shows the structure at a glance, on screen or on paper.

The W3C lists bookmarks as an advisory technique for WCAG success criterion 2.4.5, Multiple Ways, because they let readers find content in long documents without reading page by page. A contents page does the same job for people reading on paper.

PDFToolz Edit PDF Bookmarks loads the bookmarks a file already has into a list, shows page thumbnails beneath it and writes the edited list back into the PDF. It runs in your browser on Windows, Mac, iPhone and Android, without Acrobat, and the file is never uploaded. The pages themselves are not changed.

Find headings reads the text of every page and picks out lines set at least 15% larger than the body text, with no more than 20 words. The largest heading size becomes the top level, the next size level 2 and the next level 3. On pages that are not rotated, each bookmark opens just above its heading instead of at the top of the page.

It skips running headers and footers that repeat across pages, page numbers, and a lone title line in the largest size on page 1. It needs real text, so a scanned PDF must go through OCR PDF first. Headings that are bold but the same size as the body text give it nothing to detect, so add those bookmarks by hand.

Bookmarks you leave untouched keep their exact position on the page, and bookmarks that open a website keep their link. Bookmark colors and bold or italic bookmark styles are not kept. Saving an empty list removes every bookmark from the file.

The easiest bookmarks are made when the PDF is created. In Word for Windows, choose File > Save a Copy, or Save As for a file you have not saved yet, and pick PDF. Select More Options > Options, tick Create bookmarks using and choose Headings. Each Word heading becomes a bookmark in the PDF.

In Acrobat Pro, open the Bookmarks panel and go to the page you want. Select text on it, then choose New Bookmark from the panel's Options menu. The selected text becomes the bookmark's title.

Google Docs builds a document outline from your headings. Google does not document whether the PDF download keeps that outline as bookmarks, so check the side panel of the downloaded PDF and add them with a bookmark editor if they are missing.

PDFToolz Add Table of Contents writes contents pages with dot leaders, page numbers and a link on every row. Each link covers the full row, from the title to the page number. The tool fills the entry list from the PDF's bookmarks, or you type one entry per line with the page number at the end.

The contents pages take the size of the page they follow, so they match A4, Letter or any other size in the file. Long lists flow onto as many pages as they need, and every page number accounts for all the inserted pages. Top-level rows are bold when the list has sub-entries, and titles too long for one line wrap with the number on the last line.

Titles are set in Helvetica. When a title has letters outside Western European languages, such as Polish, Czech, Greek or Russian, the page uses Liberation Sans instead. Chinese, Japanese, Korean, Arabic and Hebrew titles are not supported. Page labels such as i, ii and iii are not updated for the new pages.

If you still have the source document, you can build the contents there. In Word, choose References > Table of Contents and pick an automatic style. The entries come from your headings, and you right-click the table and choose Update Field after edits. In Google Docs, choose Insert > Page elements > Table of contents, and press Refresh after you change headings.

Export to PDF afterwards and click a few rows. If they don't jump to their pages, add the contents to the finished PDF instead.

The two tools read each other's output, so you only have to describe the structure once.

Bookmarks mark where each part of a document begins, which makes them a ready-made split plan. PDFToolz Split PDF by Bookmarks starts a new file at each bookmark down to the level you choose, from top level only to level 4. It names each file after its bookmark, such as 03-Results.pdf, and each file can keep the bookmarks that point at its own pages. Pages before the first bookmark, such as a cover, become a Front matter file or join the first file.

Acrobat Pro and Acrobat Standard can split by top-level bookmarks. A contents page can't drive a split in any tool, because its rows are text and links on a page, not an outline the tool can read.

These are the problems that come up most with PDF navigation.