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ConvertBox

Compress PDF

Reduce PDF file size in your browser with balanced or high compression modes, keeping documents private while preparing them for email or upload.

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Select PDF File

You can select a single PDF file

Max file size: 100MB

or drag and drop · press Enter to browse

How to Use

  1. Upload the PDF you need to compress (scanned invoices, contracts, quotes, dossiers, or commercial proposals — up to 50MB).
  2. Click "Compress PDF" — pdf-lib and image re-optimization run entirely inside your browser.
  3. The whole process is local, so confidential documents are never uploaded to any server.
  4. You see the before-and-after size so you can decide whether the savings are worth it.
  5. Useful for fitting attachments under Gmail (25MB), corporate mail (often 10MB), tender portals, or government e-filing limits.
  6. Text, hyperlinks, and bookmarks are preserved after compression — full-text search inside the PDF keeps working.

All processing is done in your browser, and files are never sent to a server.

Frequently Asked Questions

Compression results vary depending on the content. PDFs with images typically achieve 30-70% size reduction.
Text quality is preserved during compression. The tool primarily optimizes embedded images and removes unnecessary metadata.
No, password-protected PDFs must be unlocked first before compression.
No. Compression happens entirely in your browser via WebAssembly. The file is never transmitted anywhere.
Yes — at the lowest quality setting, embedded images become visibly soft. Use the preview to balance size against visual fidelity.
Digital signatures are invalidated by any byte-level change, including compression. Compress first, then sign.
Yes, AcroForm fields remain interactive. Only embedded raster images and metadata are re-optimized.
No. All operations are processed entirely inside your browser's local sandbox using client-side APIs (like WebAssembly, pdf-lib, or HTML5 Canvas). Your files and data never leave your device.
The tool is completely free with no usage limits. However, since processing occurs in your browser's memory, we recommend keeping file sizes under 50MB (especially for heavy files like PDFs or videos) to ensure stability.
No. All tools on ConvertBox are 100% free. We do not insert watermarks, limit features, or require any registration or payment.
Yes. Once the page and its local library dependencies are loaded in your browser, the conversion logic runs completely offline without needing an active internet connection.

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