Split a large PDF into smaller files

The short answer

1. Open Split PDF and choose your PDF. Its page count and size appear next to its name.
2. Choose "By range" under "Split how".
3. Type a number next to "Or cut every", like 10, and press Cut. The parts box fills in for you: 1-10, 11-20, 21-30 and so on. Or type your own parts.
4. Press "Split into N PDFs". Every part comes out as its own PDF, all together in one ZIP file.
5. Unpack the ZIP and check each part's size before you send it.

One thing to understand before you start: Split PDF cuts by pages, not by file size. There is no "make 5 MB parts" setting. You can still get every part under a size limit, though: split by pages, check the sizes, then shrink any part that is still too big. This article shows how to pick the number of pages so that the first try usually works, and what to do when it doesn't.

Pages, not megabytes: why the parts aren't equal in size

Ten pages of one PDF can weigh far more than ten pages of another, and even within one file. Two things decide it.

What is on the pages. A page of typed text takes a few kilobytes. A scanned page is a photo of paper and can take megabytes. A report with a few colour photos in the middle has heavy pages there and light pages around them, so equal page counts don't give equal sizes.

What the pages share. Pages of a typed document share fonts. When you split, each part needs its own copy of the fonts its pages use, so the parts can add up to more than the original. The pages of a scan are separate pictures that share almost nothing, so the parts add up to about the original. Our tests show both:

So for a scan, splitting shares its size out across the parts. For a long text document, cutting it into many tiny parts makes the total bigger, though each part is still small.

Choosing how many pages to put in each part

If you need parts under a limit, a little arithmetic before you split saves a second round.

1. Read the size and page count shown next to the file's name once you add it.
2. Work out a rough size per page: the file's size divided by its pages. This is a fair guess for a scan whose pages are alike. It is less reliable for typed pages, because each part also carries its own copy of the fonts.
3. Leave room. Aim each part well under the limit, because some pages are heavier than others.
4. Test one part. Before cutting the whole file, choose Pick pages, type the first part (like 1-40), leave One PDF and save it. A single PDF isn't zipped, so its size shows right in the result.
5. Then cut every N pages with the number that worked.

An example. Say you have a 120-page scan of 60 MB to send by Gmail, which takes attachments up to 25 MB and sends bigger files as a Google Drive link. That's about half a megabyte a page, so 40 pages would be about 20 MB, with room to spare. Test pages 1-40, and if that part comes out comfortably under 25 MB, cut every 40 pages for three emails.

Parts don't have to be equal. After pressing Cut, you can still edit the parts box by hand. Move a cut to the start of a chapter, or give a section full of photos fewer pages than the rest, like 1-50, 51-65, 66-120. Each part you type becomes its own PDF, in the order you type them.

Every N pages, your own ranges, or every page

By range starts with the file cut into two halves, such as 1-10, 11-20 for a 20-page file, so a quick split in two needs no typing at all. The coloured part numbers on the cards show where each part starts and ends; pages in no part are dimmed and left out.

Splitting by chapter? The splitter doesn't cut at bookmarks or headings by itself. Open the file in our PDF Viewer, use its Bookmarks tab to jump to each chapter, and note the page number where each one starts. Then type the ranges.

The parts come in one ZIP file, named after your PDF, like report-split.zip, holding report-pages-1-10.pdf, report-pages-11-20.pdf and so on. A ZIP can hold up to 4 GB; for more, split in smaller batches. The guide covers all three ways in more detail.

Getting every part under a size limit

When several parts come back in a ZIP, the result shows the size of the whole ZIP, not of each part. So unpack it first: on Android, tap it in your Files app and choose Extract; on iPhone, tap it in the Files app; on Windows, right-click it and choose Extract All; on a Mac, double-click it. Your file manager then shows each part's size.

For each part still over the limit, pick one of these:

• Compress it. Our PDF compressor takes several PDFs at once, does them one after another and gives each its own Download button. Start with Recommended; use Smallest if that isn't enough.
• Resize it to the exact limit. Resize PDF makes the sharpest version that lands just under the size you pick, like 2 MB or 500 KB. It also takes several PDFs at once.
• Cut it again. Open that part in Split PDF and cut it in two.

Here is what those tools did in our tests, for a sense of scale:

Scans shrink a lot, because they are pictures stored sharper than they need to be. Text-heavy files shrink less, because text and fonts are kept sharp: Resize PDF couldn't take that textbook below 2.56 MB. For a text-heavy file, fewer pages per part is what helps.

Try shrinking before you split. For a scan, compressing the whole file first can mean fewer parts, or none at all. Then split the smaller copy.

Do you need to split at all?

People often split when another step would do the job better. Check which situation is yours:

On that reading point: our PDF Viewer showed the first page of a 1,000-page, 1.11 GB scan in 0.8 to 1.5 seconds in our tests, because it doesn't load the whole file first. A big file is not always a reason to cut it up.

Real results with big files

We split these files in Chromium 141, the open-source browser Google Chrome is built on, on a Linux computer with 4 processor cores and 16 GB of memory. Times are what the page reported; yours may be faster or slower.

Cutting the 117-page textbook into single pages, 117 PDFs, took 4.7 seconds. Memory, not time, is what limits big splits. Taking 10 pages out of the 400-page scan made the browser use about 1.1 GB more memory than when idle; for the 1.11 GB scan it was about 2.7 GB. We set no limit on size or pages, but your device's memory is one, so use a computer for files of hundreds of megabytes. We drew every page of every new PDF and compared it with the page it came from: all of them matched.

If the browser says "These files are too big to handle in this browser's memory", close other tabs and apps and make fewer files at a time. With a huge file, one way is to take out a big block first, like pages 1-200 as one PDF, then split that block into its parts, and repeat for the next block.

Splitting on a phone

Split PDF runs in Chrome on Android and Safari on iPhone and iPad, with nothing to install. Typing the parts is easier than tapping on a small screen, and Or cut every works just the same. The ZIP goes to your Downloads; unpack it in your Files app.

Phones have much less memory than computers. A statement, a few scanned certificates or a 50-page report should be everyday jobs; a scan of several hundred megabytes is a job for a computer. If you only have a phone, make fewer files at a time; if it still runs out of memory, the file needs a computer.

Sending the parts so they make sense

• Name them for the reader. report-pages-41-60.pdf is exact but cold. Rename them Report-part-1-of-3.pdf and so on, so the order is clear even in a long list of attachments.
• Watch the sorting. Some file managers sort names letter by letter, so report-pages-101-120.pdf can appear before report-pages-21-40.pdf. Renaming to Part 1, Part 2 avoids the muddle.
• Say what's coming. In the first email, write how many parts there are and which pages each one holds.
• Know that cross-links break. Links and bookmarks that point into another part are removed, since that page isn't in the file. In our textbook test, each half kept the bookmarks for its own pages, 17 and 18 of the 35, and 316 of 509 links still worked; the 193 that led into the other half were removed.
• Keep the original. Splitting never changes it, and the person you send the parts to can join them again with Merge PDF.

Signed documents need care: a split part no longer carries a valid digital signature, because it is a changed copy. If someone must verify the signature, send the original another way, such as a shared-drive link.

Problems and quick fixes

• A part is still too big. Compress it, resize it to the limit, or cut it in two, as in Getting every part under a size limit.
• "Together these PDFs are over 4 GB, too big for one ZIP." Make fewer files at a time, for example the first half of the parts, then the rest.
• The button says "Check the parts". A part in the box can't work, such as a page past the end. The red line under the box says which.
• The button says "This PDF has only one page". There is nothing to split. To make a one-page file smaller, compress it.
• "Locked with a password." Remove the password in your PDF reader first, then add the unlocked copy.
• You only need a few pages, not parts. Use Pick pages instead; extracting pages from a PDF walks through it.