Add Bookmarks to a PDF
Adding bookmarks to a PDF builds a clickable outline — the table-of-contents panel viewers show beside the pages — so readers can jump straight to any chapter of a long document. This tool turns a simple typed list ("Title | page", with a dash prefix for sub-entries) into genuine outline dictionaries written into the file, and can set the document to open with its bookmarks panel visible. Because the outline is stored separately from the pages, nothing about how the document looks or prints changes; the whole edit happens in your browser.
How it works
Inside a PDF, the outline is a small object graph hanging off the document catalog's /Outlines entry. Each bookmark is an outline item dictionary with a /Title string, /Parent, /Prev and /Next links that stitch siblings into a doubly linked list, /First and /Last pointers to child items, and a /Count whose sign records whether the entry displays open or closed. Navigation comes from each item's /Dest: a destination array naming a target page object and view, such as [page /XYZ left top zoom]. Because destinations reference page objects rather than bare page numbers, a correctly built outline keeps working even if pages are later inserted or removed.
This tool constructs that graph from your list. Each "Title | page" line becomes one outline item: the tool resolves the page number to the actual page object, builds a fit-page destination for it, encodes the title (using UTF-16 when it contains characters outside Latin-1, so accents and symbols survive), and wires up the /Prev//Next chain in the order you typed. A line starting with "-" is attached as a child of the most recent unprefixed entry instead: it goes into that parent's /First//Last chain, gets its /Parent pointer set, and increments the parent's /Count so viewers know the entry expands. One nesting level is supported — chapters with sections beneath them — which covers the outline depth most documents actually need.
The optional final touch is a single catalog entry: setting /PageMode to UseOutlines instructs compliant viewers to open the file with the bookmarks panel already showing — worthwhile for manuals and reports, where the outline is the intended front door. And because the outline is pure metadata, the cost is negligible: a few hundred bytes per entry, no rendering changes, no reflow, no risk to page content. The rewritten file replaces any outline the document had before, so the list you enter is the complete, final outline.
Worked example: outlining a 148-page policy manual
An HR team has policy-manual.pdf, 148 pages and 6.2 MB, with no outline at all. Working from the printed table of contents, a coordinator types 50 lines into the tool — 9 chapter entries like 7. Leave policy | 88 and 41 dash-prefixed sections like - 7.2 Parental leave | 96 — and ticks "open with bookmarks panel". Building the outline takes well under a second; the output is 6.21 MB, about 10 KB larger. Opening it in any viewer now shows the panel immediately with 9 expandable chapters, and clicking "7.2 Parental leave" jumps straight to page 96. One typo — a chapter entered as page 61 instead of 63 — was fixed by correcting two characters in the list and running the tool again, which replaced the outline wholesale.
Frequently asked questions
How do I add bookmarks to a PDF without Adobe Acrobat?
Load the PDF into the tool on this page and type one line per bookmark in the form Title | page, with a leading dash for sub-entries. The tool writes a real outline into the file, in your browser, at no cost.
What format do I use to enter the bookmark list?
One bookmark per line as Title | page number, for example Introduction | 3. Start a line with a dash to nest it under the entry above, as in - Scope | 4. One level of nesting is supported.
Are these real PDF bookmarks that work in any viewer?
Yes. The tool writes standard outline dictionaries with titles, tree links and page destinations, exactly as the PDF specification defines them, so Adobe Reader, Preview, browsers and e-readers all show the same clickable panel.
Can the PDF open with the bookmarks panel already visible?
Yes. Tick the open-with-bookmarks option and the tool sets the document's PageMode to UseOutlines, which tells compliant viewers to show the panel as soon as the file opens.
Will adding bookmarks change how my pages look or print?
No. The outline is metadata stored beside the pages, not on them, so nothing renders or prints differently. The file grows by only a few hundred bytes per bookmark.
What happens to bookmarks I already have in the PDF?
The tool replaces the existing outline with the list you enter. If you want to keep old entries, include them in your list alongside the new ones.