How to compress a PDF for email or an upload limit
Shrink a PDF to fit an email attachment or a portal’s size limit while keeping text sharp, and what to do when compression alone isn’t enough.
“Attachment too large.” “File must be under 5 MB.” A PDF that is a few pages long can still be huge, almost always because of the images inside it: scanned pages, photos or high-resolution graphics. Recompressing those images usually brings it down to a fraction of the size.
Compressing the PDF
Drop the file into Compress PDF and choose a level:
| Level | What it does | Use it for |
|---|---|---|
| Light | Photos re-encoded at high quality, capped at 2400 pixels | Anything that might be printed |
| Balanced | Photos capped at 1600 pixels; large lossless images turned into JPG | Email and most uploads |
| Strong | Photos capped at 1100 pixels at lower quality | Strict upload limits, screen reading only |
The tool shows the new size before you download, so you can try a level and step up if it isn’t small enough. Text, fonts and vector drawings are never touched, so the document stays sharp and searchable at every level.
How small is small enough?
- Email: most services cap attachments at around 20 to 25 MB, but attachments grow by about a third in transit and some company servers accept less. Under 10 MB is a safe target.
- Upload portals: limits of 2, 5 or 10 MB per file are common for job, visa and university applications. Check whether the limit applies per file or to all files together.
When compression isn’t enough
Compression only shrinks images. If the PDF is still too large, or the tool reports that there was nothing to compress, try these:
- Remove pages you don’t need. Blank scan pages, duplicate copies and instructions that came with a form all add size. Delete PDF pages removes them without touching the rest.
- Split it. If the portal allows several files, split the PDF into parts that each fit the limit.
- Rescan at a lower resolution. A scan made at 600 DPI in colour is enormous. 200 to 300 DPI in greyscale is plenty for text documents.
- Share a link. For very large files sent by email, upload the PDF to a cloud storage service and send a link instead of an attachment.
Why won’t my PDF get smaller? goes deeper into what takes up the space, including fonts and repeated images.
Locked PDFs
Encrypted PDFs, including ones that open without a password but block editing or printing, can’t be compressed. Save an unlocked copy first: in most viewers, choose Print and then Save as PDF, then compress that copy.
Several documents at once
Sending a set of documents, such as an application with an ID, a CV and certificates? Prepare documents for an online application covers getting each file into the right format and size. To send a whole folder by email, zip it first.
Common questions
What is the attachment size limit for email?
Most email services allow attachments of around 20 to 25 MB in total, but the recipient’s server may accept less. Aim well under the limit, because attachments grow by about a third when they are sent.
Will compressing a PDF make the text blurry?
No. Only the photos and scanned images inside the PDF are recompressed. Text, fonts and drawings are left exactly as they were, so they stay sharp and searchable.
Why didn’t my PDF get any smaller?
Either it has no large images to compress, or its images are already efficiently compressed. Its size may come from embedded fonts or many pages, which compression can’t reduce much.
Which compression level should I choose?
Balanced for email and most uploads. Light if the document might be printed. Strong only when you need to get under a strict limit and the document will only be read on screen.