Split PDF and Rotate PDF: What Happens Inside the File (With Test Results)
Splitting and rotating look like the simplest PDF jobs, but our tests turned up two things worth knowing: split pages can take up many times the space of the original, and rotation never touches your content.
What Split PDF gives you
Split PDF turns every page of your file into its own one-page PDF. For a multi-page file you download a ZIP containing page-001.pdf, page-002.pdf and so on, in page order; a one-page PDF simply comes back as a PDF. There is no option to choose a page range -- every page is split.
Each page file is a complete, normal PDF: in our test the text on it was still real, selectable text. Like Merge, Split does not copy the document's title from the original's properties into the new files.
Why the split pages can add up to far more than the original
This is the result that surprised us. We split a 10-page text report of 50.3 KB, which used an embedded font. The ten page files added up to 421.3 KB -- more than eight times the original -- and each single page was about 42 KB on its own.
The reason is fonts. A PDF that embeds a font stores it once and shares it between all its pages. When the pages are separated, every page file needs its own copy of the font, so the same font is stored ten times.
A scanned document behaves differently. We split a five-page scan of 3,214 KB, and the five page files added up to 3,214 KB -- almost exactly the same -- because each page's picture belongs to that page alone and nothing is shared.
| Test file | Original | All page files together | One page file |
|---|---|---|---|
| 10-page text report with an embedded font | 50.3 KB | 421.3 KB (8.4x) | About 42 KB |
| 5-page scanned document (200 dpi) | 3,214 KB | 3,214 KB (1.0x) | About 640 KB |
What that means in practice
Sending one page is still efficient: a single 42 KB page file is smaller than the whole 50.3 KB report.
But don't split a document to make it smaller overall, and don't send all the separate pages when the whole file would do -- with text documents the pages together can be several times bigger. To shrink a file, use Compress PDF instead.
To keep only some pages, split the file, then put the pages you want back together with Merge PDF, adding them one at a time in the order you want. The merged file shares its fonts again.
What Rotate PDF does -- and why it loses no quality
Rotate PDF turns every page by 90, 180 or 270 degrees. In the PDF format, page rotation is a setting stored with each page that tells the reader how to display it; the PDF standard defines it as a clockwise turn. So 90 degrees turns pages a quarter turn clockwise, 270 degrees a quarter turn anticlockwise, and 180 degrees turns them upside down.
We checked what changes inside the file. After rotating, the content of each page -- the text and drawing instructions -- was byte-for-byte identical to the original; only the rotation setting changed. The text stayed selectable and searchable, and the file size barely moved: 50.3 KB became 49.7 KB, and a 3,214 KB scan stayed at 3,213 KB.
Rotations add up. Rotating a file by 90 degrees and then rotating the result by 90 degrees again gave a total rotation of 180 degrees, so you can always rotate again if the first choice was wrong.
| What we checked | Result |
|---|---|
| Page content (text and drawing instructions) | Unchanged, byte for byte |
| Text | Still selectable and searchable |
| File size, 10-page text report | 50.3 KB to 49.7 KB |
| File size, 5-page scan | 3,214 KB to 3,213 KB |
| Rotating by 90 degrees twice | Total rotation 180 degrees |
| Which pages are rotated | All pages |
Rotating just one page
Rotate PDF always turns every page. If only one page of a scan is sideways, split the file, rotate that single page file, then merge all the pages back together in order with Merge PDF. Our guide to merging PDFs in the right order walks through the merge step.
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