Complete guide: Split PDF by size
Splitting by size can help when the recipient accepts multiple files. A single oversized page cannot be made to fit by splitting.
When to split instead of compress
Compression can only go so far, especially for scan-heavy documents. Splitting preserves whole pages and their order, but cannot make a single oversized page smaller.
Splitting is also useful when recipients prefer smaller files, when a PDF is too large to upload, or when your organization enforces strict attachment policies.
PDFThin lets you choose a target size and returns a ZIP containing ordered parts. This removes the guesswork from manual splitting.
How PDFThin builds size‑safe parts
PDFThin checks the actual size of optimized page ranges and looks for parts that fit your target. It splits between whole pages, not within a page.
If even one optimized page exceeds the cap, splitting can fail. Try a higher target, stronger compression or a new scan, then inspect the result.
On successful processing, you get a ZIP containing ordered PDF parts. The cap applies to each PDF part, not the entire ZIP; the ZIP may exceed that cap.
Choosing the right target size
For email attachments, use a preset: Gmail 25 MB, Outlook 20 MB, Outlook.com 25 MB. If your provider is strict, choose a smaller custom target to allow for encoding overhead.
For uploads, choose the platform's actual per-file cap. Check that it accepts multiple PDF parts; if only one file is allowed, splitting is not a substitute.
PDFThin keeps the page order intact across parts so you can reconstruct the document easily.
Best practices
Keep the original file. Extract the ZIP and inspect the PDF parts in order. Send parts separately where necessary to stay within the total message limit as well.
If you need a single file instead of parts, try the email‑ready optimizer first. It will only split when compression can’t reach your target.
Start here: Split PDF by size.
Split by size FAQ
Does splitting change page order?
No. Parts are created in order and labeled accordingly.
Can I still compress before splitting?
Yes. PDFThin optimizes each part, and you can also use Email‑ready first.
What output do I get?
A ZIP containing ordered PDF parts if processing succeeds. The target applies per PDF part, not to the ZIP total; a single oversized page can prevent a successful split.