Compress PDF Online — Reduce File Size for Free
Optimize and reduce your PDF's file size. Uses Ghostscript when available for maximum compression — completely free.
What is PDF Compression?
PDF compression is the process of reducing a PDF file's size by optimizing its internal structure, re-encoding embedded images at lower resolutions, stripping unused metadata, and applying stream compression to content objects. A smaller PDF file is faster to upload, easier to email, takes less storage space, and loads more quickly in browsers and PDF viewers.
BestToolHub's PDF Compressor uses a two-stage approach. When Ghostscript is installed on the server, it is used first — this provides professional-grade compression by downsampling high-resolution embedded images to 150 DPI (screen/ebook quality) while retaining excellent readability. If Ghostscript is not available, a PHP-based fallback re-processes the document with stream compression enabled.
Note: Compression results depend heavily on your source file. PDFs with many high-resolution images see the best reductions (often 40–70%). PDFs that consist primarily of text, or that have already been compressed, may see little to no reduction — in that case the tool will tell you so honestly rather than returning a larger file.
How to Compress a PDF File
- Click Browse File or drag and drop your PDF into the upload zone above.
- Wait for the file to appear in the list below the upload area.
- Click Compress PDF Now to start the optimization process.
- The tool tries Ghostscript first, then a PHP fallback if needed.
- Your optimized PDF will download automatically — or you'll see a message if no reduction was possible.
Why Compress Your PDF?
Email-Friendly
Smaller files pass through email attachment size limits easily.
Faster Uploads
Compressed PDFs upload to cloud drives and websites in less time.
Save Storage
Reduce disk usage when storing large collections of PDF documents.
Secure Processing
Your file is processed on our server and deleted after download.
Completely Free
No limits, no subscription, no account. Always free to use.
No Software
Works in any browser without plugins or desktop apps.
Frequently Asked Questions
The reduction depends entirely on your source file. PDFs with large, unoptimized images (photos, scans) can see reductions of 40–70% when Ghostscript is available. PDFs that are already optimized — such as those generated by modern PDF printers or LibreOffice — may see little or no reduction. If your PDF cannot be made smaller, the tool will tell you rather than returning a larger file.
When using Ghostscript, the /ebook setting resamples embedded images to 150 DPI — excellent for reading on screen and printing at normal sizes. Text and vector graphics are never degraded. If you need to preserve very high-resolution images (e.g., for professional print), use a desktop tool with a /prepress quality setting instead.
If your PDF is already fully optimized (all streams compressed, images already at low DPI), there is nothing further the tool can reduce. We return an honest error rather than serving you a file that is the same size or larger. This is by design — other tools that always return a "compressed" file are often just returning the original unchanged.
You can upload PDFs up to 100 MB. For very large files, processing may take slightly longer. All uploaded files and the compressed output are permanently deleted from our server as soon as your download completes.