Compress PDF
Reduce PDF file size for email, forms and uploads. Free, no limits, and your files never leave your device.
or drop files here
Processed on your device – files are never uploaded
Your file is ready
Created on your device. Nothing was uploaded.
Continue with another tool
Large PDFs are hard to email, slow to upload and often too big for online application forms. PDF4U makes them smaller by resizing and re-compressing large images – which is where most of the size of a scan or photo-heavy PDF usually is – and by rewriting the file's internal structure more efficiently.
Everything happens in your browser, so even confidential documents stay on your device. How much smaller a file gets depends on what is inside it: scans and PDFs full of photos often shrink by half or more, while text-only PDFs that are already well optimized may hardly change. PDF4U never gives you a file that is bigger than the original.
Tips to reduce PDF size
- Start with “Recommended”. If a form still says the file is too big (for example over 200 KB or 1 MB), try “Extreme compression”.
- Need an exact result? Open “Advanced settings” and set the image resolution (dpi) and JPEG quality yourself – free, like every level.
- Printing in black and white anyway? Tick “Convert to grayscale”: colour photos and colour text become gray, which saves even more space.
- Remove pages you don’t need with Remove PDF pages before compressing – every page you drop makes the file smaller.
- Our PDF compressor shrinks images and tidies the file structure, but it doesn’t rewrite fonts or text.
How to compress a PDF
Select your PDFs
Click “Select PDF files” or drop one or more PDFs onto the page.
Choose a compression level
“Recommended” gives a good balance. Pick “Extreme compression” for the smallest file or “Less compression” to keep images sharper. Optionally convert to grayscale or set the resolution and quality under “Advanced settings”.
Compress
Click “Compress PDF”. Your browser compresses the files on your device – nothing is uploaded.
Download
Check the new size and click “Download”. Several files can be saved together as a ZIP.
Frequently asked questions
How much smaller will my PDF get?
It depends on the content. Scanned documents and PDFs with many photos usually shrink a lot, often by half or more. PDFs that contain mostly text, or that were already compressed, may only get a little smaller. If a file can’t be made smaller, you get the original back unchanged.
Will compressing reduce the quality?
Text, vector drawings and fonts are never changed, so they stay perfectly sharp. Only large photos are resized and re-compressed. Choose “Less compression” if image quality matters most, “Extreme compression” if size matters most, or set the exact resolution and JPEG quality under “Advanced settings”.
Is it safe to compress PDFs with PDF4U?
Yes. Your files are compressed by your own browser and are never uploaded to a server, so nobody else can see them.
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 whose images are already low resolution. PDF4U also leaves some image types untouched to avoid damaging them, such as black-and-white scans in special formats and CMYK images.
Can I compress a password-protected PDF?
PDFs that open without a password but have restrictions (for example on printing) are compressed and keep their protection. If a PDF needs a password to open, remove it first with Unlock PDF, then compress it.
Is there a file size limit?
No. The only limit is your device's memory. Very large files (hundreds of megabytes) work best on a computer; on phones they can be slow.
Can I compress a PDF to black and white?
Yes. Tick “Convert to grayscale”. Photos are turned gray and re-compressed, and coloured text and drawings become gray too, which often makes the file noticeably smaller. Gradients and a few special colour types stay as they are.