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By Everyday Tools Editorial Team • Last updated 2026-11-09

How to Compress a PDF

A PDF that will not fit in an email is usually big for one of three reasons: big photos, pages saved without packing, or extra data tucked into the file. Here is how to tell which one it is, and what to do about each.

What makes a PDF big

Text takes almost no room. A page of plain text is a few kilobytes — our 5-page test PDF, made of text only, was 2,227 bytes in total. What makes PDFs big is pictures. A single phone photo saved at full size can add several megabytes, and a scanned document is really a set of photos, one per page. The second cause is how the file was saved: some apps pack the text and structure tight (called object streams), and some do not, which can leave a file much bigger than it needs to be. The third cause is extra data — a title, author, and other file details, plus leftover pieces from editing — which adds a little on top.

Step 1: re-save the PDF in a tighter form

Start with the easy win. Open the compress PDF tool, add your file, and press Compress PDF. It re-saves the file with object streams and strips out the extra details. Then look at the before and after size it prints. On a text-only test file of 2,227 bytes, the saving was 0% — the file was already packed tight, so there was nothing to squeeze. On a file saved without packing, the same step can cut a real share of the size. Either way, you see the true result before you keep the file.

Step 2: shrink the photos inside it

If the file is still too big, the photos are the problem, and re-saving alone will not fix them. The fix is to make the photos smaller before they go into the PDF. As a guide, a photo-like 800 by 600 test image saved as JPG at quality 0.95 was 339.1 KB; the same image at quality 0.70 was 112.7 KB — 66.8% smaller, and still fine to look at. So: shrink each photo with the image compressor, or resize it with the image resizer (800 pixels wide is plenty for a photo in a document), then build the PDF again from the smaller photos. If the PDF came from a scanner, check the scan settings first — scanning at 150 DPI instead of 300 DPI cuts the file to about a quarter of the size, and text stays readable.

Step 3: drop pages you do not need

Every page costs room, and scanned pages cost the most. If only some pages matter, pull them out with the split PDF tool — for example, pages 2 to 3 of a 5-page file — and send just that part. Our test showed pages 2 to 3 coming out as a 1,298-byte file from a 2,227-byte whole. It is a simple step, and it is often the one that gets a file under an email limit.

What does not help

Zipping a PDF rarely helps much, because the text inside it is already packed — a zip of a PDF usually saves only a few percent. Renaming the file changes nothing. And be wary of any tool that asks you to upload the file first: a copy of your document sits on someone else's server, even if only for a minute. The tools on this site work in your browser, so the file never leaves your device at all.

How small should you aim for?

Most email systems accept attachments up to 20 or 25 MB, but many work inboxes are set lower. A good target is under 10 MB for an emailed PDF, and under 2 MB for a form upload or a web page. If your PDF is a scan, aim for 150 DPI and JPG quality around 0.70 to 0.80 for the pages — readable, and far smaller than a 300 DPI scan.

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