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Lizely

Split PDF by Size

Split one local PDF into consecutive parts measured against a maximum serialized file size, without uploading the document.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose a non-empty PDF no larger than 25 MiB.
  2. 2.Enter the maximum generated size per part from 0.01 to 25 MiB.
  3. 3.Split the document, review any oversized single-page warning, and download each numbered part.

About Split PDF by Size

Split PDF by Size divides one local document into consecutive PDF parts using a maximum output-size target. Choose a non-empty PDF up to 25 MiB, enter a target from 0.01 to 25 MiB, and select Split PDF by size. The browser copies pages into candidate documents, serializes each candidate, measures its actual byte length, and starts a new part before the candidate would exceed the target. The source and generated bytes remain inside the current browser tab and are never uploaded to Lizely.

The tool uses page order as an unbreakable rule. If pages 1 through 4 fit together and adding page 5 crosses the limit, the first download contains pages 1 through 4 and the next begins with page 5. It does not reorder pages, skip pages, duplicate pages, or divide a single PDF page into visual pieces. The sum of the page counts shown for all parts therefore equals the structural page count of the input.

Size decisions are based on newly serialized PDF files, not on a proportional estimate from the source file size. PDF resources can be shared across pages, compressed differently, or copied into a new document with different overhead. Measuring each candidate catches those effects more honestly than assuming every page consumes an equal fraction. A part that is accepted by the planner has a generated byte length at or below the chosen target at the time it is built.

A single page cannot be split by this workflow. If one copied page alone produces a PDF larger than the target, that page is kept in its own part and the download is visibly labeled as exceeding the target. This exception prevents silent page loss and prevents an infinite retry loop. Choose a larger target or use a dedicated compression workflow if a receiving system rejects that oversized single-page file.

The target uses mebibytes: one MiB equals 1,048,576 bytes. Decimal input is accepted to three places. The minimum 0.01 MiB is useful for deterministic testing and very small documents, while the maximum matches the tool's bounded local-file workflow. Browser and operating-system download displays may round the same byte count differently, so the tool also shows each generated part size for review.

Each output is a fresh PDF made by copying the selected source pages. Page boxes, rotation, vector artwork, text, and embedded raster content are retained to the extent supported by the existing copy operation. Advanced document-level structures such as bookmarks, scripts, attachments, portfolio relationships, named destinations, and cross-part links may not preserve their original semantics after pages are separated. Inspect important interactive files before relying on the parts.

Files that are empty, larger than 25 MiB, encrypted, damaged, mislabeled, or unsupported produce a visible error. Password protection is not bypassed. Changing the file or size target revokes prior download URLs so an old result cannot be confused with the current settings. A job identifier also prevents a slower earlier operation from replacing a newer result.

This tool does not compress images, optimize fonts, linearize a PDF, guarantee a particular email-provider acceptance decision, or force every output under the target when a single page is already too large. It is best for page-boundary splitting with measured output bytes. For equal page counts use Split PDF in Half; for manual ranges use Extract PDF Pages; for reducing content size use a dedicated compression tool after its dependency and quality requirements have been evaluated.

Methodology & sources

Validate one bounded PDF and a decimal MiB target, greedily append consecutive page indices, serialize each candidate PDF to obtain its real byte length, finalize the previous group when the candidate crosses the target, preserve an oversized single page as a flagged one-page part, then rebuild and expose numbered downloads.

Frequently asked questions

Are all parts guaranteed to be below the target?
Every multi-page part is measured before acceptance, but a single page that already exceeds the target is kept alone and clearly flagged.
Does splitting preserve page order?
Yes. Parts contain consecutive pages in the original order, and their page counts add up to the source total.
Why can output sizes differ from a simple source-size estimate?
Copied PDF pages have serializer overhead and may share or duplicate resources differently, so the tool measures generated bytes instead of estimating.
Is the PDF uploaded?
No. Page copying, serialization, measurement, and download creation run locally in the browser.

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