A long PDF without bookmarks forces readers to scroll blindly to find the section they need. Most PDF readers have a bookmarks/outline panel built in — the problem is usually that the document itself never had any bookmarks added to populate it.
What bookmarks actually are
A PDF bookmark is a named link in the file’s outline that jumps straight to a specific page when clicked — the same idea as a clickable table of contents, but shown in the reader’s sidebar rather than printed on a page. They don’t change the document’s content at all, just its navigation. They come up constantly for contracts with numbered exhibits, technical manuals with dozens of sections, and court filings — plenty of e-filing systems flat-out require a bookmarked PDF before they’ll accept it.
Worth knowing before you start: a bookmark you build this way jumps to the top of the page you picked. It’s not anchored to a specific paragraph, image, or zoom level the way some desktop apps (Acrobat, PDF Expert) let you pin a bookmark to a selected block of text. For “click this, land on that page,” that distinction doesn’t matter. If you were hoping to bookmark one sentence halfway down a page, it won’t get you closer than the top of that page.
Adding them
Create Bookmarks builds this outline visually:
- Upload your PDF — every page renders as a thumbnail.
- Click the thumbnail for each section you want to jump to (a chapter start, a new topic, an appendix).
- Type a name for that bookmark.
- Repeat for every entry, then download.
No need to know anything about the PDF format internally — you’re just clicking pages and naming them.
Flat list, not a nested outline
Desktop tools like Acrobat let you drag one bookmark under another to build a multi-level tree — a chapter with sub-chapters nested underneath it. This tool doesn’t do that: every bookmark you add lands at the same top level, in one flat list.
If you want the sidebar to read like it has sub-sections anyway, a numbering trick works: name entries “2. Chapter Two”, then right after it “2.1 Setup” and “2.2 Usage”. They’re still flat, technically, but the numbering makes the grouping obvious to anyone browsing the outline panel. It’s not real hierarchy, just a naming convention that reads like one.
A note on existing bookmarks
If the PDF already has an outline (say, it was exported from a word processor with headings), adding new bookmarks through this tool replaces the old outline with the one you just built — this tool doesn’t read or display whatever bookmarks are already there, so you’re building the list from scratch either way. If you’re happy with the existing bookmarks and only want to add a couple more, it’s better to check whether your source document (the Word file, etc.) can regenerate the PDF with those additions already included.
If you just want to see what’s already in the outline before deciding, run the file through Split PDF by Bookmarks first — it doesn’t touch your original file, and the split pieces it hands back are named after each existing bookmark, which is a quick way to read out the current titles and their page order before you commit to overwriting them here.
Pairing with other structure tools
Once your document has a clean bookmark outline, Split PDF by Bookmarks can turn each top-level entry into its own separate file — handy for breaking a long report into standalone chapter PDFs after you’ve marked out the sections.