A long PDF with no bookmarks makes people scroll. A 200-page manual, a thesis, a contract bundle with twelve schedules: readers want to click "Schedule 7" in the side panel and land on it. That clickable list is the PDF's bookmarks, and if your file doesn't have any, you can add them yourself.
Create bookmarks adds bookmarks, nests them into chapters and sections, and edits the ones a file already has. It runs in your browser, and the file isn't uploaded.
What a PDF bookmark actually is
Inside the PDF format, bookmarks are called the document outline. It's a small tree of entries stored apart from the pages. Each entry has a title, a destination (usually a page) and, optionally, child entries nested under it. The viewer reads that tree and draws it in a sidebar: the Bookmarks panel in Adobe Acrobat Reader, the table of contents view in Preview's sidebar on a Mac, the outline button in Chrome's PDF viewer.
Two things follow from that. Bookmarks don't change anything printed on the pages, so adding them can't move your text or put a mark on a page. And they have nothing to do with the contents page printed near the front of your document. That page is just text, sometimes with links on it. The outline is separate data, and a file can have one, the other, both or neither.
Why so many PDFs have no bookmarks
Bookmarks are normally generated at export time from the headings in the source document. Microsoft Word does it when you use the built-in Heading styles and leave the option to create bookmarks from headings switched on in the PDF export settings. Lots of other routes produce nothing:
- Scanning. A scanner makes pictures of pages and has no idea where a chapter starts.
- Printing to PDF. A "print to PDF" driver only sees printed pages, so the heading structure is lost.
- Documents where the headings are ordinary text made bigger and bold, rather than real heading styles.
- Combining files with a tool that throws away each file's outline.
If you still have the source document and it uses proper heading styles, exporting again is usually the quickest fix for a long file. When you don't have the source, or the PDF is a scan or a bundle of separate documents, you build the outline by hand.
Adding bookmarks step by step
- Open Create bookmarks and add your PDF. If it has a password, you'll be asked for it. Bookmarks already in the file load into the list, and the bar says "(existing bookmarks loaded)".
- Click the thumbnail of the page where the first section starts.
- Type a title in the box at the top and press Enter, or click "Add bookmark on page 1" (the number follows the page you selected). Leave the title empty and the bookmark is simply called "Page 1".
- Repeat for each section. A new bookmark goes straight after the selected one in the list. With nothing selected, it's slotted in by page order.
- Arrange the list (see the next section), then click "Apply changes".
- Download the result, saved as bookmarked-yourfile.pdf.
Clicking a bookmark in the list moves the page selection to its target, which is a quick way to check them all. To fix a wrong target, select the bookmark, click the right thumbnail, and use the "Point the selected bookmark to page 5" link above the thumbnails. You can also type a number in the small "p." box on the row.
Building chapters and sections
A flat list is fine for a dozen entries. Past that, nest them. Each row in the "Bookmarks" list has small buttons:
- The ↑ and ↓ buttons move the bookmark up or down among the entries at its level.
- The → button nests it under the bookmark above, so it becomes a child of that entry.
- The ← button moves it out one level.
- The plus button adds a nested bookmark under that row, pointing to the selected page.
- The × button deletes it. If it has nested bookmarks, they go with it.
The pattern I'd use for a report: add every chapter and section in page order first, then go down the list pressing → on each section so it tucks under its chapter. Two levels suit most documents, three at most for a technical manual.
Under "More options" there are two settings for how the file opens. "Show bookmarks panel on open" is ticked by default and asks the viewer to open the sidebar with the outline showing. "Expand all" and "Collapse all" decide whether nested entries start open or folded. Some viewers ignore both settings, so treat them as requests rather than guarantees.
Fixing bookmarks a file already has
The tool isn't only for files with no outline. PDFs exported from other software often arrive with bookmarks that are nearly right: a typo, an entry called "Untitled", a heading that points one page early. Fix a title by typing in its row, change the target page, delete the junk, or press "Remove all" and start again.
Bookmarks you leave alone keep their original styling (colour, bold or italic) and whatever action they had. Only the links between the entries are rewritten. A bookmark that points outside the file, such as a web address, shows an empty page box and is kept exactly as it was unless you give it a page number.
What the tool won't do
A bookmark made here opens a page. It can't target a heading halfway down that page, and it can't open a web link. For most documents that's close enough: the reader lands on the right page and looks down.
It also doesn't read your headings and suggest bookmarks. You type each one, which for a book-length file takes a while. If you have a Word source with real headings, re-exporting will be faster.
Every bookmark needs a title. If one is blank when you click "Apply changes", you'll see "Every bookmark needs a title." and nothing is saved until you fix it.
Do your page work first. Delete, reorder and merge pages before you add bookmarks, so you aren't fixing targets twice. The outline is also what Split by bookmarks reads, so a clean set of top-level bookmarks lets you cut a bundle back into its parts later.
Check it in another viewer
When the file downloads, open it in something other than your browser, ideally the app your readers use. Acrobat Reader and Preview both show the outline in their sidebars. Click every top-level bookmark once and make sure each lands on the page you meant. A bookmark that opens the wrong chapter is the kind of small error people remember.
Also useful: Merge PDF · Split by bookmarks
