PDF Compressor

Free online PDF compressor to reduce PDF file size without uploading documents to ToolsLibrary servers. Choose Low, Medium, High, Custom (DPI and JPEG quality), or a local AI Recommended preset. Batch-compress multiple PDFs, unlock password-protected files in the browser, compare original vs compressed size, preview results, download individually or as a ZIP, and cancel long jobs. Pages are rasterized and JPEG-encoded into a new PDF — image-heavy files usually shrink most; already-efficient text PDFs may see smaller gains.

How to Use the PDF Compressor

Upload one or more PDFs, choose a compression level, and download smaller files in your browser. Pages are rasterized and JPEG-encoded — image-heavy PDFs usually shrink most.

  1. Upload one or more PDF files with drag-and-drop or the file picker (PDF only).
  2. Choose a compression level: Low (best quality), Medium (balanced), High (smallest file), Custom (DPI and JPEG quality), or AI Recommended (local heuristic).
  3. If a PDF is password-protected, enter the password and unlock it before compressing.
  4. Select Compress PDFs and wait while each page is processed. You can Cancel a long job.
  5. Compare original vs compressed size on each file, Preview the result if you want, then Download individually. With more than one result, use Download ZIP.
  6. Use Reset when you are finished to clear files and revoke temporary preview URLs.

How compression works

This tool rasterizes each page at a target DPI, JPEG-encodes it, and rebuilds a new PDF. Image-heavy and scanned documents usually shrink the most. Mostly-text PDFs that are already efficient may change only a little — or occasionally grow — because pages become images.

Choosing a level

  • Low — higher DPI and JPEG quality; best when readability matters most.
  • Medium — practical default for everyday sharing and email.
  • High — smallest files; may look softer on fine text or photos.
  • Custom — set DPI and JPEG quality directly.
  • AI Recommended — local suggestion from bytes per page; not a cloud upload.

Common mistakes

  • Expecting every PDF to shrink by a large fixed percentage.
  • Running High compression repeatedly on the same output and losing readability.
  • Not checking Preview after aggressive settings.
  • Uploading non-PDF files (only PDF is accepted).

Limitations

Compression is lossy page rasterization, not a guarantee of selectable text, bookmarks, or original metadata. Very large or complex PDFs may be slow or hit browser memory limits. Upload size and file-count caps apply.

Privacy

Compression runs entirely in your browser. PDF bytes are not uploaded to ToolsLibrary servers. Passwords stay in the page session for decrypting locally. Temporary preview URLs are revoked when you close preview, reset, or leave.

FAQ

How do I compress a PDF?

Upload your PDF, choose Low, Medium, High, Custom, or AI Recommended, then select Compress PDFs. Download the compressed file, or Download ZIP when you compressed more than one.

What compression levels are available?

Low keeps higher DPI and JPEG quality for better fidelity. Medium balances size and readability. High prioritizes smallest files. Custom lets you set DPI and JPEG quality. AI Recommended is a local heuristic from file size and page count — not cloud AI.

How much can a PDF be reduced?

It depends on the document. Image-heavy and scanned PDFs usually shrink more. Already-optimized or mostly-text PDFs may change only a little. The tool shows original vs compressed size after each job — there is no fixed percentage guarantee.

Can I reduce PDF size without losing quality?

Not with a zero-loss guarantee. This tool rasterizes pages and uses JPEG encoding, which is lossy. Use Low for higher fidelity, Medium for everyday sharing, and High when smallest size matters most. Always preview important files.

Why did my PDF size barely change?

The PDF may already be efficient, or it may be mostly text. Rasterizing such files sometimes yields small savings or even a slightly larger file. Try another level or keep the original if savings are not worth it.

Are my PDFs uploaded to a server?

No. Compression runs entirely in your browser. Files are not sent to ToolsLibrary servers for compression.

Can I compress multiple PDFs?

Yes. Batch upload is supported (up to the site file-count limit). Compress them together, then download each file or a ZIP of all compressed PDFs.

What is AI Recommended compression?

A local heuristic looks at file size and page count to suggest Low, Medium, or High settings. It is not cloud AI and does not upload your document.

Can I compress password-protected PDFs?

Yes. Enter the document password when prompted. The password is used only in your browser to decrypt and compress.

How does PDF compression work here?

Each page is rendered (rasterized) at a target DPI, encoded as a JPEG image, then placed into a new PDF. That shrinks image-heavy scans most; mostly-text PDFs may shrink little or grow slightly because pages become images.