What is PDF Compressor?
PDF Compressor is a free browser-based PDF tool powered by PDF-lib. Your documents are processed entirely in your browser and never sent to any server. Works with any standard PDF file. No Adobe Acrobat or software installation needed.
This tool lets you reduce pdf file size in your browser without installing any software or creating an account. Everything runs directly in your browser for maximum privacy. Your files and data never leave your device.
Use it for quick tasks at any time from any device — desktop, tablet or mobile. No subscription, no ads, no limits.
⚡
Instant results
No server processing or wait
🔒
100% private
Files stay on your device
💰
Always free
No subscription or fees
📱
Mobile ready
Works on any device
How to use PDF Compressor
- Upload your PDF file — drag and drop or click to browse
- Select compression level: low, medium or high depending on your needs
- Click Compress and watch the file size reduction percentage appear
- Download your compressed PDF — typically 40–80% smaller for image-heavy files
Why use OnlineToolsPlus?
PDF tools on OnlineToolsPlus use PDF-lib — a JavaScript PDF engine that runs locally in your browser. Your documents are never uploaded to a server, which means no privacy risk for sensitive contracts, financial documents or personal files. With 25+ free PDF tools covering merging, splitting, compressing, editing and converting, you have a complete PDF toolkit at no cost.
Frequently asked questions
How much can PDF compression reduce file size?
It depends on the content. PDFs with many high-resolution images can often be reduced by 70-90%. Text-only PDFs have little to compress and may only reduce by 10-20%.
Will compression make text harder to read?
No. Compression targets embedded images, not text. Text rendering in PDFs is vector-based and remains crisp regardless of compression level.
Is the compression lossless?
No. PDF compression reduces image resolution inside the PDF, which is a lossy process. The result looks identical on screen but may show slightly softer images at very high print magnification.
Why did compression barely reduce my PDF?
Your PDF is likely mostly text with minimal embedded images. There is simply less image data to compress. This is common for text documents, reports written in Word, and simple spreadsheets.
Can I compress a PDF that is already compressed?
Yes, but with diminishing returns. If the PDF was already optimized by its creator, further compression may only achieve a small additional reduction.
Does compression affect PDF/A or signed PDFs?
Compressing a digitally signed PDF will invalidate the signature because the file content changes. For PDF/A archival files, compression may affect compliance. Use the PDF/A converter after compression if needed.
More PDF Tools
Last updated: April 11, 2026
View all 200+ free tools →