How to compress a PDF and reduce its size
Did an upload portal reject your file because it’s too big, or did an email bounce? That usually happens with scanned PDFs or PDFs full of photos, because every page is a high-resolution image.
Filezain’s Compress PDF re-saves each page as an image at the quality you choose, inside your browser and without uploading the file.
When you need it
- A PDF scanned with a phone or scanner is over the upload limit.
- A catalogue or presentation with many photos.
- Sending a file through WhatsApp or email with a size limit.
- Saving space when archiving many files.
Steps
- Open Compress PDF and choose your file.
- Move the quality slider: a lower number means a smaller file and lower quality.
- Press the convert button.
- Compare the new size with the original before sending.
- If the text looks blurry, compress again at a higher quality.
Tips
- Start with the default quality (0.6); it suits most scanned documents.
- Compression turns pages into images, so text can no longer be selected or copied. Keep a copy of the original.
- If your PDF is text only (typed on a computer, not scanned), it may not get smaller and can even grow. Compression mainly helps image-based PDFs.
- To shrink it further, delete unneeded pages first with Organize / Delete Pages.
Common problems and fixes
- The result is bigger than the original.
- Your PDF is probably text-based, not scanned. Compression won’t help here — send the original.
- The text became blurry.
- Compress again with a higher quality such as 0.75 or 0.8.
- I can’t copy text after compressing.
- That’s expected: the pages are now images. Use the original when you need to copy text.
- Compression is slow.
- Very long files take time because every page is processed on your device. Split the file and compress each part.
Frequently asked questions
Is my file uploaded to a server?
No, all compression happens inside your browser.
What’s the best quality setting?
Between 0.5 and 0.7 for most files; go higher if the file has small text.
Does it work with protected files?
Remove the password first with Unlock PDF.
Why is the text no longer searchable?
Because the tool re-saves each page as an image to reduce the size.