How to split a PDF by its bookmarks or chapters
Updated 19 August 2026
To split a PDF by chapters, use its bookmark outline rather than page numbers. UnboundPDF’s Split by Bookmarks reads the outline tree, lets you choose the level to cut at (parts, chapters or sections), names each file after its heading, keeps the pages before the first bookmark as a named “Front matter” file, and carries each chapter’s own bookmarks into its file. It runs in your browser; the PDF is not uploaded.
Split a PDF using its own bookmarks — pick a level, keep chapters whole, and nothing before the first bookmark gets lost.
UnboundPDF is a free suite of 43 PDF and image tools that run entirely in your browser — merge, split, compress, edit text, OCR in 126 languages, redact, sign, convert and archive to PDF/A. Your document is read and written by the page on your own device; there is no document-upload endpoint in the core tools, no account, no watermark and no daily cap. Every result can be checked — with the Network tab, or with the Document Passport the Workspace writes for a chain of steps.
- Open Split by Bookmarks and drop in the PDF. The outline tree appears with every heading.
- Choose a level — Level 1 for parts, Level 2 for chapters, deeper for sections. The count beside each level is the number of files you will get.
- Untick any section you do not need, or override a single node.
- Check the preview: two bookmarks that point at the same page are listed together as one file; pages before the first bookmark appear as “Front matter”.
- Split and download the ZIP. Each file is named after its heading and keeps its own bookmarks.
What the tool reads
It does not search the text for “Chapter”. It reads the PDF’s own outline — the bookmark panel your reader shows on the left — including nested entries, named destinations and bookmarks that point at a page by reference rather than number. That is why it works on a 700-page standard with a three-level outline as well as on a ten-chapter novel: the structure is already in the file.
Split by Bookmarks is the tool described here — it runs in your browser, and the PDF is not uploaded.
Choosing the level
Every level option shows how many files it would produce, and that number is the real count after grouping — if two bookmarks land on the same page, they become one file, and the label says so. Cut at the chapter level for a book; go deeper when you need each section as its own handout. You can untick individual nodes, so “every chapter except the appendices” is two clicks.
The pages before the first bookmark
Cover, title page, copyright, contents — most outlines start after these. A naive splitter drops them silently. Here they are collected into a named “Front matter” file by default; untick it if you do not want it, and the choice is visible in the list rather than a page count that quietly comes up short. Every page of the input ends up in exactly one output file unless you chose otherwise.
Two bookmarks, one page
Outlines often have a part heading and its first chapter on the same page. Instead of losing one or making an empty file, the tool lists both names together and writes one file for them. The preview shows exactly which headings were combined.
Each chapter keeps its own bookmarks
The output files are not bare page ranges. Each one carries the sub-outline that belonged to it — open “Chapter 7” and its sections are still in the bookmark panel, pointing at the right pages of the new, shorter file. Nested counts are rebuilt correctly at every level.
Stopping part-way
Press Stop during a long split and nothing partial is produced: no half-written ZIP, no stray files. Run it again when you are ready.
When to split by page range instead
If the PDF has no outline at all — many scans and exported reports do not — there is nothing to read. Use Split PDF with page ranges — the step-by-step is in splitting a PDF without uploading it — or Split by Size if an attachment limit is the constraint. To reorder or delete pages first, Organize PDF; to put chapters back together later, Merge PDF (how-to). The short how-to for e-books is split a book PDF into chapters; the privacy case for keeping all of this local is in merge PDFs privately.
Frequently asked questions
How do I split a PDF into chapters?
If the PDF has bookmarks, open it in Split by Bookmarks, choose the chapter level, and download the ZIP — one file per chapter, each named after its heading and carrying its own bookmarks. If it has no bookmarks, split by page range instead.
What happens to the cover and table of contents?
Pages before the first bookmark are collected into a named “Front matter” file by default. You can untick it; the choice is visible, not a silent drop.
Can I split only some chapters?
Yes. Untick the nodes you do not need, or override a single node. The file count beside the level updates to the real number.
Do the chapter files keep their bookmarks?
Yes. Each output file carries the part of the outline that belongs to it, with page references rebuilt for the new file.
The split says two bookmarks share a page — is that a problem?
No. They are listed together and written as one file, so nothing is lost or duplicated. The preview names both headings.