How to make a PDF smaller for email or an upload form
Updated 16 October 2026
A PDF that is too large to email or to attach to an online form is almost always large because of its pictures: scanned pages, photos, or images placed at a much higher resolution than any screen or printer needs. Text and drawings take up very little space. So the most effective way to shrink a PDF is to make its pictures smaller, and leave the text alone.
Make the PDF smaller in four steps
- Open Compress PDF and drop your PDF on the box, or choose it from your device. If the file is protected with a password, you are asked for it.
- Choose how strongly to compress (see below). Balanced is right for most files.
- Select Compress PDF. A large file takes a few seconds; the work happens in your browser, so the file is not uploaded anywhere.
- Download the result. It is named after your file, for example
report-compressed.pdf, and the page shows how much smaller it got.
Which level to choose
| Level | Pictures are saved at about | Good for |
|---|---|---|
| Smallest file | 100 dpi | Reading on a screen, email attachments |
| Balanced | 170 dpi | Screens and ordinary office printing |
| Best quality | 250 dpi | Documents you will print, photos that matter |
“dpi” means dots per inch on the printed page. A full A4 or Letter page at 100 dpi is about 1,200 pixels high, which is sharp on any screen. If the result looks too soft, run the original again with the next level.
What stays the same
Text stays text: you can still search it, select it and zoom in without blur. Links, bookmarks and form fields are kept, because the tool changes the existing document instead of rebuilding it. Drawings, charts and diagrams are left exactly as they are, since compressing them as photos would blur their sharp edges.
One thing does change: if the PDF has a digital signature, any change to the file makes that signature invalid. Keep the original if the signature matters, and compress a copy.
If it barely gets smaller
Some PDFs are already compact. A report made in a word processor is mostly text and fonts, and there is little to remove. You will see a short note, and if the compressed file would not be smaller, you simply get the original back.
Other ways to get under a size limit:
- Send fewer pages. Split PDF can cut the file into parts, or save just the pages someone needs.
- Shrink photos before they go into the PDF. If you are making a PDF from photos, compress the images first, then turn them into a PDF with Image to PDF.
- Check the limit. Many email services stop at about 20 to 25 MB per message, and online forms often accept only a few megabytes. A PDF of scanned pages at “Smallest file” usually takes a few hundred kilobytes per page.
Why your file stays private
Many online PDF compressors upload your document to their servers to process it. Here, the compression runs in your browser on your own device: the file and its name are never sent anywhere. You can check this yourself, as described in how it works.