Compress PDF

What this tool does

Compress PDF offers two methods. Strong compression re-renders every page as a JPEG at the resolution and quality you choose, which shrinks scans dramatically. Lossless mode re-saves the PDF with compressed object streams and can strip unused data and metadata while keeping text intact.

Scanned documents and phone-camera PDFs are often far larger than they need to be: a 20-page scan at 600 DPI can easily exceed 50 MB, which is too big for most email services and many upload forms. Reducing the resolution of those page images to 100-150 DPI usually keeps them perfectly readable on screen while cutting the size by 80% or more.

Strong mode renders each page with pdf.js at the DPI you choose, encodes it as a JPEG and places it on a page of the same size in a new PDF. This is ideal for scans and image-heavy files, but text becomes part of the image, so it can no longer be selected or searched, and links and form fields are lost. Lossless mode keeps everything as it is and only rewrites the file structure using compressed object streams, optionally rebuilding the document and removing metadata. Both run entirely in your browser.

How to use Compress PDF

1. Drop one or more PDF files onto the upload area.
2. Pick a method: Strong (rasterise) for scans and photos, or Lossless (optimise) for text documents.
3. In Strong mode choose a preset (Screen 72 DPI, eBook 110 DPI, Print 150 DPI, High 220 DPI) or fine-tune Resolution and JPEG quality.
4. Optionally turn on Convert to greyscale for black-and-white documents.
5. Press Compress PDF and follow the progress bar page by page.
6. Compare the before and after sizes shown for each file and download the ones that got smaller.

Tips for better results

• For scanned text, 110-150 DPI with 60-75% quality is a good balance; 72 DPI is readable on screen but poor in print.
• Greyscale saves extra space on scanned letters and forms where colour adds nothing.
• If a text-based PDF made by a word processor grows in Strong mode, use Lossless mode instead; vector text is already compact.
• Rebuild document in Lossless mode is most effective on files that were edited many times, since old revisions are discarded.

Common use cases

• Shrinking a phone-scanned contract so it fits under an email attachment limit.
• Meeting a 2 MB upload cap on a government or university application portal.
• Archiving years of scanned receipts without filling up cloud storage.
• Stripping author metadata and unused objects before publishing a report.

Common mistakes to avoid

• Using Strong mode on a document that must stay searchable or editable; the output pages are images.
• Choosing a DPI higher than the original scan, which cannot add detail and only makes the file bigger.
• Compressing an already-compressed PDF repeatedly; each JPEG pass loses a little more detail.
• Expecting large savings from Lossless mode on PDFs that are mostly photos; only rasterising reduces image data.