How to compress a PDF and keep it readable
Last updated: 1 November 2026
To make a PDF smaller without making it hard to read, open Compress PDF, keep the “Recommended” level and click “Compress PDF”. Text, fonts and vector drawings are not changed. Only large photos are resized and re-compressed, and the file's internal structure is rewritten more efficiently.
This guide is for you if a PDF is too big to email, slow to upload or rejected by an online application form. It covers the three compression levels, the advanced settings, what results to expect and what to do when one file is simply too large.
Step by step
- Open the compress tool. Go to Compress PDF in your browser. You don't need an account or sign-up.
- Select your PDFs. Click “Select PDF files” or drop one or more PDFs onto the page.
- Choose a compression level. Keep “Recommended” for a good balance. Pick “Extreme compression” for the smallest file or “Less compression” to keep images sharper.
- Adjust the advanced settings if needed. Tick “Convert to grayscale” if you print in black and white anyway. Under “Advanced settings”, you can set the image resolution (dpi) and JPEG quality yourself.
- Compress the files. Click “Compress PDF”. Your browser compresses the files on your device, and nothing is uploaded.
- Check the size and download. Look at the new size and click “Download”. If you compressed several files, you can save them together as a ZIP.
What compression changes and what it keeps
Most of the size of a scan or a photo-heavy PDF is usually in its images. The tool resizes and re-compresses those large images and tidies up the file structure. It does not rewrite fonts or text, so words, lines and vector drawings look the same as before.
The three levels
- Recommended: a good balance between file size and image quality. Start here.
- Extreme compression: gives the smallest file. Use it when size matters most, for example when a form still rejects the file.
- Less compression: keeps images sharper. Use it when photo quality matters most.
Advanced settings
- Resolution (dpi): a lower value makes photos smaller in size and less detailed.
- JPEG quality: a lower value saves space but shows more compression artefacts in photos.
- Convert to grayscale: colour photos, colour text and drawings become gray, which saves more space. Gradients and a few special colour types stay as they are.
All levels and settings are free.
What results to expect
How much smaller a file gets depends on what is inside it, so the tool can't promise a specific result. You also can't set a target file size. Choose a level, check the new size, and try a stronger setting if the file is still too big.
- Scanned documents and PDFs with many photos usually shrink a lot.
- PDFs that contain mostly text, or that were already compressed, may get only a little smaller.
- Some image types are left untouched to avoid damaging them, such as black-and-white scans in special formats and CMYK images.
- The tool never gives you a file that is bigger than the original. If it can't make the file smaller, you get the original back unchanged.
Tips for a small, readable PDF
- Compress once. A file that has already been compressed usually gets only a little smaller the second time. Choose a stronger level for the original file instead.
- Keep the original. The compressed PDF is saved as a new download. Keep the original file in case you need full-quality images later or want to try a different setting.
- Split instead if one file is huge. If a long document is still too big, use Split PDF to cut it into parts with “Every N pages” or “Custom ranges”, then compress each part if needed.
- Building a PDF from photos? In JPG to PDF, choose A4 with a small margin, then run the result through Compress PDF.
- Use a computer for very large files. Files of hundreds of megabytes work best on a computer. On phones, they can be slow.
Tools used in this guide
Frequently asked questions
Will compressing reduce the quality of my PDF?
Text, vector drawings and fonts are never changed, so they stay sharp. Only large photos are resized and re-compressed. Choose “Less compression” if image quality matters most, or set the exact resolution and JPEG quality under “Advanced settings”.
How much smaller will my PDF get?
It depends on the content. Scans and photo-heavy PDFs usually shrink a lot. Text-only or already compressed files may get only a little smaller.
Can I compress a PDF to a specific size?
No, you can't set a target file size. Try “Extreme compression”, or lower the resolution and JPEG quality under “Advanced settings”, then check the new size before you download.
Why didn't my PDF get smaller?
Some PDFs are already as small as they can be, for example files with only text or files with low-resolution images. Black-and-white scans in special formats and CMYK images are left untouched to avoid damaging them. In that case, you get the original back unchanged.
Are my files uploaded when I compress them?
No. Your browser compresses the files on your own device, so they are never uploaded to a server and nobody else can see them.
Is there a file size limit?
There is no fixed limit. The only limit is your device's memory. Very large files work best on a computer, and they can be slow on phones.
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