LocalPDFlab

Compress a PDF

Everything happens on your device. Your file never touches a server.

Drop a PDF here, or click to choose one

Larger files may take longer, especially on mobile.

Enter PDF password

Enter the password to open.

How to compress a PDF

  1. 1

    Choose your file

    Drop a PDF into the box or select one from your device.

  2. 2

    Pick a compression mode

    Choose High Quality or Flatten Scans.

  3. 3

    Adjust settings

    For Flatten Scans, choose a resolution and image quality.

  4. 4

    Compress and download

    Compress the PDF locally, then download the result.

How PDF compression works

High Quality performs a fast structural rewrite: it removes unreachable objects, compresses eligible structural objects, and preserves existing page content and image data. It is best for digital PDFs, though already-efficient files may shrink only slightly. Flatten Scans redraws every page as a compressed JPEG at your chosen resolution, so it is intended for scanned or image-heavy documents. Before processing the full file, LocalPDFLab samples representative pages and keeps your original if the result is unlikely to be smaller. Both methods run entirely inside your browser.

Match the mode to the document

Start with High Quality for reports, contracts, slide decks, and other PDFs exported from software. It keeps selectable text, vectors, links, and form fields. Use Flatten Scans for pages that are mainly scanner or camera images. It replaces each page with a white-background JPEG, so search, accessibility structure, annotations, and interactive fields are not carried into the new file.

Working toward a file-size limit

The 120 DPI setting is a practical starting point for screen reading. Try 72 DPI for a smaller review copy, or 150 DPI when fine print needs more clarity. Check several pages before sharing. If readable compression still cannot meet an email or portal limit, use Split PDF to create smaller parts instead.

Frequently asked questions

Which mode should I use?

Use High Quality for most digital PDFs. It performs a fast, content-preserving structural cleanup, though savings may be modest. Use Flatten Scans only for scanned or image-heavy documents when a smaller file matters more than search, links, forms, accessibility, and vector sharpness.

Is there a file size limit?

There is no server-side upload limit. Browser memory and on-device safety limits still apply, especially when Flatten Scans must render hundreds of pages. Large jobs are more reliable on a desktop browser.

Why was no smaller file created?

Digital PDFs store text, fonts, and vectors compactly, so replacing every page with JPEG can make them larger. Efficiently encoded scans can behave the same way. LocalPDFLab tests representative pages and keeps your original unless flattening provides a useful reduction.

Can I stop compression?

Yes. Use Cancel while compression is running. Processing stops on your device and your original file remains unchanged.

Will existing digital signatures remain valid?

Usually not. Compression rewrites the PDF, which can invalidate cryptographic signatures. Keep the signed original and compress an unsigned copy when signature validity matters.

Next steps

Related PDF tools

Choose another private, browser-based tool for the next step in your document workflow.