Compress PDF Online – Reduce File Size
Reduce the size of a large scanned PDF while keeping it readable.
🔒 Your file is processed inside your browser. It is never uploaded or saved.
What is Compress PDF?
Email limits, job portals and government websites often refuse files above a few megabytes. This tool shrinks a heavy PDF by redrawing each page as an optimised picture, which works especially well for scans and photo-based documents. You pick one of three quality levels, see the size before and after, and keep the original untouched. All processing happens on your own device, so confidential files are never uploaded.
How to compress a PDF online
- Select the PDF you want to make smaller, or drop it onto the upload box.
- Open the Quality list. “Better quality” keeps pages crisp, “Balanced” suits most files, and “Smallest file” gives the strongest reduction.
- Press Start and wait while each page is redrawn. A long document can take a minute on a phone.
- Read the size note below the button, which compares the old and new sizes, then download the file ending in -small.pdf.
When Compress PDF is useful
Email attachments
Bring a scanned contract under the size limit of your mail provider without splitting it into parts.
Online application forms
Many portals cap uploads at 1 or 2 MB. Try Smallest file for ID scans, certificates and photo-heavy pages.
Archiving scans
Save storage by shrinking a folder of scanned receipts and letters.
Sharing on messaging apps
Send a smaller file over a slow mobile connection.
Tips for better results
Be aware of the trade-off. Compression here turns every page into a picture, so the text in the new file cannot be selected or searched. If you need searchable text, run OCR PDF on the result afterwards. A PDF that is already text-only and tiny may not get smaller, and in that case the tool tells you to keep your original. For a tight target such as 100 KB, start with Balanced, check the result, then try Smallest file, and consider splitting the file or deleting pages you do not need. There is no fixed output size, because it depends on your content.
Why use PDFToolkit
When you compress a PDF online with PDFToolkit, the work stays on your own device. Your contracts, ID scans and invoices are processed in the browser and are never sent to a server.
- Private: no upload, nothing saved.
- Free: no sign-up, no daily limit and no watermark.
- Fast: no waiting for files to travel over the internet.
- Everywhere: Windows, Mac, Linux, Android and iPhone.
Frequently asked questions
How much smaller will my PDF be?
It depends on the content. Scanned and photo-heavy PDFs often shrink a lot, while text-only files may change very little. The tool shows the exact before and after sizes.
Why can I not select text in the compressed PDF?
Pages are saved as images to reduce size. Use OCR PDF if you need the text back, or keep the original for editing.
Which quality setting should I choose?
Start with Balanced. Move to Smallest file only if the result is still too big, and to Better quality if small print looks blurry.
Is the original file changed?
No. Your original stays on your device. The tool creates a separate file with -small added to the name.
What if the compressed file is larger than the original?
That can happen with files that are already optimised. The tool then advises you to keep the original.
Is it safe to compress private documents here?
Yes. The work is done in your browser and nothing is uploaded, so the file never reaches our servers.