Guide
Building a clickable outline for a long PDF
Bookmarks, also called the outline, are the clickable list of chapters and sections in a PDF reader’s sidebar. In a 200-page report, they are the difference between scrolling for a minute and jumping straight to section 4.2. Documents exported from good authoring software usually have them; scanned books, merged files and PDFs from many web apps don’t. This editor adds them, fixes them and can generate them for you.
Start with what’s there
Open a PDF and its existing bookmarks are listed with their titles, levels (shown by indentation) and target page numbers. If some bookmarks open a website or run an action instead of a page, the tool tells you how many; those can’t be edited here and are not kept when you save.
Generate bookmarks from headings
Click Generate from headings and the tool reads every page, finds text that is set larger or bolder than the body text, and turns each heading into a bookmark. The largest headings become top-level entries, smaller ones are nested underneath. It works well on reports, manuals, theses and e-books exported from Word, Google Docs, LaTeX or InDesign.
Afterwards, check the list:
- Remove entries that aren’t real headings, such as a bold line in a table.
- Shorten long titles; sidebars are narrow.
- Adjust levels so chapters are at the top and sections below them.
Editing by hand
- Type in the title box to rename a bookmark; titles can use any language.
- Change the page number to retarget it.
- Move in or out a level with the indent buttons. A bookmark can be at most one level deeper than the one above it, as in any outline.
- Move up or down to reorder, delete with the cross.
- Add bookmark appends a new entry after the last one, pointing at the next page.
If you lose track, Back to the original restores the bookmarks the file came with.
After saving
The new outline is written in the standard PDF format, so it works in Adobe Acrobat and Reader, Chrome, Edge and Firefox, Preview on a Mac, and phone PDF apps. Each bookmark opens at the top of its page, and the file is marked to show the bookmark panel when it’s opened, so readers notice the outline straight away.
Bookmarks and accessibility
People who use screen readers or keyboard navigation rely on structure to move through long documents. A good outline is one of the simplest improvements you can make to a PDF’s accessibility, alongside a proper title, which you can set with the PDF Metadata Editor.
When pages change
Bookmarks point to specific pages. Tools that rebuild a document from its pages, such as merging or organising, drop the outline. Add or fix bookmarks as the last step. Tools that edit in place, like Insert Blank Pages and Reverse PDF Pages, keep bookmarks attached to their pages.
Using bookmarks to split
Once a document has a good outline, Split PDF by Bookmarks can cut it into one file per chapter, named after the bookmarks.
A worked example: a scanned book
A researcher has a 240-page scanned book with no bookmarks.
- Run it through OCR PDF so the pages contain text.
- Open the result here; Generate from headings finds the larger chapter titles.
- Remove a few false hits and fix two page numbers.
- Save: the book now opens with a chapter list in the sidebar.
Checked against the current version of the PDF Bookmark Editor on .