A different question from Split PDF
Split PDF answers "how many pages in each part". This answers a different question that comes up just as often: a portal caps uploads at 10 MB, an email provider caps attachments at 25 MB, and a two hundred page scanned document needs to become however many files fit under that number — which is not a page count you can know in advance, because PDF pages are wildly uneven in weight. A scanned photograph page can outweigh fifty pages of plain text.
Why it cannot just divide the page count evenly
If a hundred-page document needs four parts, dividing into four groups of twenty-five pages each produces four files of very different sizes whenever the content is uneven — which scanned documents almost always are. This tool works the other way round: it adds pages to the current part one at a time, and the moment adding the next page would push that part's actual saved size over your limit, it closes the part and starts a new one with that page.
Each part is measured after being saved, not estimated from page count, because PDF compression makes the relationship between pages and bytes hard to predict any other way. That is also why this is slower than a page-count split — every candidate page requires actually rebuilding and re-saving the file being measured.
Common limits, for reference
| Destination | Typical limit |
|---|---|
| Most email providers | 10 MB per attachment |
| Gmail | 25 MB per attachment (and total message size) |
| Outlook.com / Exchange | 20–25 MB depending on the organisation |
| Older government or bank portals | as low as 100 KB–2 MB |
| Modern web upload forms | typically 10–50 MB |
When in doubt, split to a size noticeably under the stated limit — email servers and portals routinely count a small overhead against the same cap, and a file that lands at exactly 25.0 MB against a 25 MB limit sometimes still bounces.
What happens to a single heavy page
Occasionally one page — usually a high-resolution scanned image — is heavier on its own than the limit you set. There is no way to split a single page across two files, so that page becomes its own part, marked as oversized, and the split continues from the page after it. The practical fix, if it matters, is to compress the source document first: Compress PDF re-renders image-heavy pages at a lower resolution, which usually brings a single oversized page back under any reasonable limit.
Getting the parts back out
- Each part downloads on its own, named
-part1,-part2and so on in page order — sending them in sequence in an email thread is usually clearer than one ZIP. - All parts are also offered together as a single ZIP, useful when they are going into a shared folder rather than an inbox.
- Recombining them afterwards, if you ever need the whole document back, is exactly what Merge PDF does — feed the parts back in, in order.