Split a Large PDF Into Chapters: From the Bookmarks to One File per Chapter

The short answer

There is no chapter button in Split PDF. It cuts at the page numbers you give it, so the job takes two steps. First, find the page where each chapter starts, using the bookmarks of the PDF. Then type the chapters as ranges in Split PDF under Custom ranges: 1-20, 21-40 and so on.

We tried it on October 23, 2026, with a 120-page A4 book made in LibreOffice. It had six chapters of 20 pages, a photo in each, a bookmark for each chapter, and 2,006,153 bytes. Six ranges gave six PDFs in 0.56 seconds, in headless Chrome on a 2023 Mac laptop.

Split PDF does not split a file by its bookmarks; our comparison with Sejda lists that among the gaps. It takes one PDF at a time, up to 300 MB, and makes up to 500 parts.

Find where each chapter starts

Bookmarks, which some programs call the outline or the table of contents, are a list of headings, each pointing to a page. Clicking a heading opens its page, and that page number is what Split PDF needs. Split PDF itself does not show bookmarks.

On our site, PDF Viewer does. Open More settings, set Side panel to Outline, then open the PDF. Our book listed its six chapter titles, without page numbers. Clicking Chapter 4 turned the counter to “Page 61 of 120”, so chapter 4 starts on page 61. The side panel appears on screens at least 1024 pixels wide. A PDF without bookmarks gets “This PDF has no outline.”

On a Mac, Preview has the same list. Apple's Preview guide, read on October 23, 2026, says: “Show a document’s table of contents (if it has one): Choose View > Table of Contents.” Its View > Bookmarks lists something else, the pages you bookmark there yourself.

In Adobe Acrobat, the list sits in a side panel. Adobe's page on PDF bookmarks, read the same day, says: “Click the Bookmarks button to open the Bookmarks panel.” With no bookmarks at all, page through the thumbnails. Split PDF counts pages from the first page of the file. If the front pages are numbered i, ii, iii, printed page 1 comes later.

Type the chapters as ranges

Drop the PDF into Split PDF. It opens on With scissors, one of four ways to split: numbered thumbnails of every page, with a ✂ between them to cut. For chapters, choose Custom ranges. Before you type, it says “Type ranges, for example 1-3, 4-8.”

We typed 1-20, 21-40, 41-60, 61-80, 81-100, 101-120 into Ranges. Commas, semicolons and line breaks all separate ranges, and an en dash counts as a hyphen. The settings showed “Result: 6 files” and listed the parts from “Part 1 · pp. 1–20” to “Part 6 · pp. 101–120”.

Pages you leave out go into no file, so a cover or an index can stay behind. A page can also sit in two ranges, as the hint under the field says: “A page can be in several parts.”

If every chapter has the same length, Every N pages does the job with one number. With 20, we got the same six files under the same names. When the page count does not divide evenly, the last part comes out shorter, so chapters of different lengths need ranges.

Six files, their names and the ZIP

The page summed up the result as “6 files: 1–20 · 21–40 · 41–60 · 61–80 · 81–100 · 101–120. All together as one ZIP, or each separately.” Under it were two buttons, Download all (ZIP) and Download one by one (6).

The ZIP is called pulsarkit-split.zip unless you type another name in the “ZIP name” field. Inside, each part is named after the book and its pages: book-6-chapters-pages-1-20.pdf, book-6-chapters-pages-21-40.pdf and so on. To give the files chapter titles, rename them after the download.

One range gives one PDF, with no ZIP around it. A single page, such as 7, gets a name like book-6-chapters-page-7.pdf.

The box “Put the chosen ranges into one file” does the opposite: every range goes into one PDF, named book-6-chapters-split.pdf. With our six ranges, that was the whole book again, 120 pages. It suits two chapters kept together, such as 21-40 and 81-100. For a single chapter, Extract pages also makes one new PDF from the pages you list.

How much the parts weigh

The book keeps its six photos and two fonts in one shared set that every page refers to. A part takes from that set only the photos its own pages show. The fonts are the exception: every part gets both of them whole.

More parts, more copies of the fonts. With Every N pages left at 1, the page offered 120 files.

Whether the parts add up to more or less than the original depends on how the PDF was made. A 20-page text document printed to PDF from Chrome, 148,121 bytes, split into two parts of 111,564 bytes together, a quarter smaller.

If one chapter is too heavy to email, Split by size cuts it into parts under a limit you set.

What the parts keep and lose, and how typos are caught

Pages are copied into each part as they are, with their text, fonts and images. Bookmarks come along too: a part keeps the bookmarks that point to its pages, and they open those pages inside the part. So each chapter file keeps its chapter's bookmark.

A link that jumps to another page keeps working when that page is in the same part; a link to a page that went to another part is removed. A link to a website keeps working.

A typo is caught before anything is cut. We added 115-130 for our 120-page book, past its last page. The status turned to “Needs fixing”, and the download button stayed off. The message names the missing page: “Page 130 does not exist, this PDF has 120 pages.” A backwards range gets its own: “Range 9-4 starts after it ends.”

Split PDF runs in your browser, and the book is not sent to our server. To continue in another tool, PulsarKit may store a local copy of your input or result in this browser. It can remain after you close the tab or restart the browser. Clear PulsarKit’s site data to delete it.