How to Compress a PDF Online
A practical guide to reducing PDF file size while balancing readability, image quality, and compatibility.
Quick answer
To compress a PDF, open the PDF Compressor, select your file, choose a compression level, and download the result. Scanned and image-heavy PDFs shrink the most. Always compare the output and keep the original.
Why PDF files become large
PDFs often contain scanned pages, photographs, screenshots, embedded fonts, and other assets. A document with a few text paragraphs can stay small, while a scanned document can become many megabytes because every page contains image data.
Compression works by reducing the amount of data required to represent those assets. The best settings depend on whether you need maximum readability, a smaller attachment, or a balance between the two.
How to compress a PDF
Open the PDF Compressor, select your document, choose a compression level, and start processing. When processing finishes, compare the original and output sizes before downloading.
- • Use a stronger setting when file size is the main priority.
- • Use a balanced setting for everyday sharing and email attachments.
- • Use a clearer setting when screenshots or scanned text need to remain easy to read.
Which compression level should you pick?
If you are unsure, start with the balanced option. Most documents end up noticeably smaller with no visible change on screen. Only move to a stronger level if the file is still above the size limit you are aiming for.
Compress once from the original file. Compressing an already compressed PDF again usually gives smaller gains and can make images look worse each time.
What to check after compression
Open the resulting file before sending it. Check small text, scanned pages, tables, signatures, and any pages that contain important images. A smaller PDF is not automatically a better PDF if important information becomes difficult to read.
Frequently asked questions
- Does compressing a PDF reduce its quality?
- It can. Stronger compression lowers image quality to save space, so check small text, tables, and scanned pages before sharing the file.
- Why is my PDF still large after compression?
- PDFs made of high-resolution scans or photos are mostly image data. A light setting may not shrink them much, so try a stronger level and check readability again.
- Is it safe to compress a PDF in the browser?
- With browser-side processing, the selected file is handled on your device instead of being sent to a remote processing server. Check the privacy page for details.