Split PDF pages in half
Halving PDF pages turns every page into two — a left and right half, or a top and bottom half — by duplicating each page and giving each copy a crop box covering one half. It is the standard fix for scanned book spreads that hold two facing pages per image, and it runs locally in your browser with no upload. A 100-page file of double-page spreads becomes a 200-page file of single pages in correct reading order.
Note the difference from neighboring tools: Split PDF divides a document between pages into separate files; this tool divides each page itself through the middle into two pages. If you only need to trim margins rather than cut pages in two, use Crop PDF.
How it works: two copies of the page, two crop boxes
A PDF page can define several nested boundary rectangles. The media box is the full extent of the page; the crop box is the region a viewer actually displays and prints. The crop box may be any rectangle inside the media box, and viewers treat it as the visible page. This tool exploits that: to halve a page, it imports the page twice into the output document and assigns each copy a different crop box — for a left/right split, the first copy is cropped to the left half (x from 0 to width/2) and the second to the right half (x from width/2 to width). Top/bottom splits work the same way along the y axis, with the top half emitted first to preserve reading order.
Nothing is rasterized and nothing is geometrically transformed; the content streams are untouched, so scanned images keep every pixel and any OCR text layer stays aligned with its image. Since both halves reference the same underlying page resources, the output does not double in size the way a naive copy would — the heavy scan image of each spread is stored once and displayed twice through different windows.
The honest trade-off of the crop-box method: the full spread still exists inside each output page, merely windowed. That is invisible in every normal viewer and printer, but a tool that resets crop boxes could show the other half again. For a private book scan this is irrelevant; if you were halving to hide content, you would want true removal via redaction instead, which flattens pages so hidden data is genuinely gone.
Worked example: a scanned paperback, two pages per image
A 1998 paperback scanned on a flatbed at 300 dpi: 148 landscape images, each an open two-page spread, saved as a 96.4 MB PDF. Every spread is 17.4 × 11 inches of scan holding book pages of roughly 8.5 × 11 each. Running the left/right split produces 296 portrait pages in about four seconds. Output size: 97.1 MB — nearly unchanged, because each spread image is stored once and windowed twice, and only page dictionaries were added. The result reads page 1, page 2, page 3… in order on a tablet, instead of forcing constant sideways zooming across spreads. One caveat found on inspection: the book’s title spread had artwork crossing the gutter, and it came out divided across output pages 1 and 2 — exactly what the straight middle cut predicts.
Halving PDF pages — frequently asked questions
How do I split a scanned book PDF so each page stands alone?
Choose the left/right split on this page: every scanned spread becomes two portrait pages in reading order. A 150-spread scan turns into a 300-page PDF that reads like the physical book.
Does halving PDF pages cut the actual image data in half?
No. Each half-page is the full original page with a crop box showing only one half, so the underlying data is intact. That also means the file roughly doubles its page count without shrinking, and an uncropped view could reveal the hidden half.
Which split direction do I need, left/right or top/bottom?
Use left/right for landscape pages holding two portrait pages side by side, which covers book and magazine spreads. Use top/bottom for portrait pages stacking two landscape halves, such as 2-up handouts printed to PDF.
What happens to text that crosses the middle of the page?
The cut is a straight line at the halfway point, so anything straddling it is visually divided between the two output pages. Book spreads are safe because the gutter is empty, but check pages with full-width tables or images first.
Can I undo the split or get the original spreads back?
Your original file is never modified, so just keep it. And because the halves are crop-box views of complete pages, resetting the crop boxes in a PDF editor would restore each spread from the output too.