A scanned book is a single 400-page file, and nobody wants a 400-page file: not the reviewer who needs chapter six, not the e-reader that chokes on it, not the portal with a 10 MB limit. Splitting it well depends on one question — does the document know where its chapters are? — and the answer decides which of the methods below to use.
First, find out what the PDF knows
Open the file in any viewer and check two things:
- Does it have bookmarks (an outline in the side panel)? A publisher’s PDF usually does; a scan almost never does.
- Can you select text? If so, it has a text layer — either born-digital or OCR’d. If dragging across a paragraph selects nothing, it is a bare scan.
Bookmarks give you the easiest split. A text layer gives you a good one. A bare scan gives you the manual options, or a quick trip through OCR PDF to earn the better ones.
The methods
Split PDF and Split PDF by size or bookmark between them cover every case. All of them run in your browser; the book is never uploaded.
By bookmarks
Each top-level bookmark starts a new part, named after it. The cleanest result when the outline is real. The tool explains the rule before it runs and warns when bookmarks do not point at usable pages.
By page-start words
Give it the word a chapter’s first line begins with — Chapter, Part, Section, a case name — and every page whose text starts that way opens a new part. Needs a text layer. Excellent for OCR’d scans, where bookmarks never existed but the typography did.
By blank separator sheets
Photocopy pilers and scanning services insert a blank page between documents. Filozy renders each page at low resolution and detects the near-empty ones, splitting there. Works on bare scans with no text layer at all. Review the detected boundaries: a nearly blank final page of a chapter can look like a separator.
By custom ranges
Type the page ranges yourself — 1-12, 13-40, 41-88. The fallback that always works, and the right choice when you have a table of contents in front of you.
Every N pages
A stack of scanned two-page forms becomes one file per form with every 2 pages. Arithmetic, no inspection of the content.
Into N equal parts
Hand a manuscript to four reviewers. Also arithmetic.
By target file size
For upload limits: parts that each stay under a size you choose, measured from the actual output. See the caveats in the FAQ — sizes are approximate by nature, and a single oversized page cannot be split further.
Step by step for a scanned book
- Straighten and trim with Auto crop if the scan has heavy borders; smaller pages split and compress better.
- OCR it with OCR PDF if you want chapter detection by words, searchability in the parts, or both.
- Open Split PDF. Choose page-start words and enter the chapter word, or blank separators for a bare scan, or type the ranges from the table of contents.
- Review the boundaries the tool proposes. Fix any it missed or invented.
- Decide whether the groups should stay separate files or be combined into one extracted PDF of the chapters you care about.
- Save. Parts download individually or as a ZIP.
- Open two or three parts and check the first and last pages of each. Keep the original.
Naming and order
Parts are numbered in document order and named from the source file plus the bookmark or range, so they sort correctly in a folder. If you rename them, keep a leading number; 06 Chapter Six.pdf survives any file manager, Chapter Six.pdf ends up between Chapter Seven and Chapter Ten.