Adding Bookmarks to a PDF: Make a Long Document Easy to Navigate

Open a fifty-page report in a PDF reader and the side panel is empty. Open a good one and it shows a list: introduction, method, results, appendices, each a click away from its page. That list is the document's bookmarks, also called its outline. It is cheap for an author to include and saves every reader time, yet scans, printed-to-PDF files and packets merged by older tools usually have none.

What a bookmark is

A bookmark is a title, a page to jump to, and a place on that page. Bookmarks can be nested, so a chapter can hold its sections, and a group can start open or closed. They belong to the document rather than to a page, which is why a tool that rebuilds a file from its pages has to carry them over on purpose, and many do not.

Adding them with the Bookmarks tool

Drop the file into the Bookmarks tool. Any bookmarks it already has appear as a list. Each row has a title, a page number and a few buttons: Up and Down to reorder, Indent and Outdent to nest, Add below and Delete. A small preview shows the page the selected bookmark points at, so you can check the number before you save. Only the bookmarks change; the pages and everything else in the file stay as they were.

Pasting a table of contents

If the document has a printed contents page, it is quicker to type it in as text than to build the list by hand. Under "Import or copy as text" write one bookmark per line as the title, a bar, and the page, with two spaces for each level of nesting:

Introduction | 1
  Background | 2
Method | 5
Results | 9

The tool tells you which line is wrong, for example a page past the end of the file, and imports nothing until every line reads. "Show current bookmarks as text" does the reverse, which is a handy way to copy an outline from one document to another.

What is not kept

A bookmark's text colour and bold or italic style are not kept, and neither is a bookmark that opens another file or runs a script; a bookmark that points at a page that does not exist is also left out. Bookmarks that open a web address are kept, though you can move or delete them but not change the address. Before you save, the tool counts each of these in your file so there are no surprises. A bookmark you do not touch opens exactly where it did before; one you point at a different page opens showing the whole page. Bookmarks you bring in with "Import or copy as text" are new, so they open showing the whole page.

Merging without losing them

The merge tool keeps bookmarks. Each file's own bookmarks are carried over and pointed at the right pages of the merged file, nested under one bookmark named after the file, so a packet of several documents opens with one entry per document even if none of them had bookmarks of its own. Untick "Add a bookmark for each file" to keep the bookmarks in one flat list instead.

Reordering and splitting

The organize tool keeps bookmarks too. Each one moves with its page, so reversing a file or dragging a chapter to the front leaves the list pointing at the right places, in the same order as before. A page you duplicate keeps its bookmark on the first copy. When you add pages from another PDF, that file's bookmarks are nested under one bookmark named after it.

A bookmark whose page you delete is removed, and so is its title. That is deliberate: a title can quote the page it points at ("Salary details"), and a deleted page should not leave its heading behind in the file. Any bookmarks nested under it move up a level. The done panel says how many were kept and how many were left out.

The split tool gives every part only the bookmarks for its own pages, numbered from the part's first page, whether you split by ranges, every N pages, bookmarks or size. Cutting pages in half is the one exception worth knowing: each bookmark points at the first half of its page, and its saved zoom is dropped because it was set for the whole page. If a file ends up with a bookmark in the wrong place, the Bookmarks tool is the quickest way to fix it.

Everything here runs in your browser. The file is read and rewritten on your device, and the titles, which can quote your document, are never stored or sent anywhere.