Your textbook PDF has 12 chapters, each with a bookmark. You want one file per chapter. Setting 12 ranges manually is fiddly and error-prone if you miscount a page.
The PDF already knows where the chapters are. Flint reads the bookmark tree and splits at those exact points.
How bookmark splitting works
Open split PDF, drop your textbook, choose 'split at bookmarks'. Flint shows your bookmark tree and lets you pick which level to split at — usually top level (chapters). Each top-level bookmark defines a split point: pages from this bookmark up to the next become one output file.
Named outputs from bookmark text
Output files inherit names from bookmarks: 'Chapter-01-Introduction.pdf', 'Chapter-02-Methods.pdf'. No 'output-1.pdf' confusion — you can identify each chapter at a glance in the downloaded ZIP. Special characters are sanitised for filesystem safety.
Choose your split depth
If your bookmarks have nested structure (chapters > sections > subsections), you pick the depth. Split at level 1 for one file per chapter. Level 2 for one file per section. Level 3 for fine-grained per-subsection split. Flint shows the tree so you can preview before splitting.
When bookmarks don't exist
If your PDF has no bookmarks, this method won't work. Add bookmarks with edit PDF first, or use range-based splitting and type the page ranges directly. For PDFs exported from Word, regenerating with 'Create bookmarks from headings' checked gives you a bookmarked file in one step.
FAQ
What if two bookmarks point to the same page?
Flint merges them into one split. The output for that section contains the page that both bookmarks reference.
What about empty bookmark entries (placeholders)?
Empty bookmarks (no page target) are skipped. They don't create empty output files.
Can I preview before splitting?
Yes. Flint shows the bookmark tree with the page range each split would produce. Adjust before downloading.
What if a bookmark target is mid-page?
PDFs bookmark at page level. The split happens at the start of that page, regardless of where on the page the bookmark anchor sits.
Let the bookmarks do the work. Split at bookmarks and skip the range typing.