How it works
Add a PDF and choose how to split it. “Every page” makes one PDF per page. “Every N pages” cuts the document into equal parts, for example chapters of 10 pages. “Custom ranges” makes one PDF per range you type, such as 1-3, 4-9, 10-, where “10-” means page 10 to the end.
The page previews show which part each page goes into before anything is saved. Pages that aren't in any range are dimmed and left out.
Pages are copied exactly as they are, using the open-source pdf-lib library in a background worker: text stays selectable, and nothing is re-compressed or watermarked.
Downloading the parts
Several parts download together as one ZIP, or one at a time from the list. Files are named after the original and numbered by page, for example report-pages-01-03.pdf and report-page-04.pdf, so they sort in order.
Fonts and images used on many pages are stored in every part that needs them, so the parts together can be larger than the original. On very large documents Vimorby stops and tells you if the parts would not fit in your device's memory.
Your files are processed by your own browser, inside this tab. Nothing is uploaded, so there is no server copy to delete, and the page keeps working if you go offline after it loads.