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How to compress a PDF (free, lossless)

Shrink a PDF without touching its quality — in your browser, with no upload and no file-size limits. Your document never leaves your device.

1. Open the PDF

Open your file in the editor, or use the Compress PDF page — there, the compressed copy downloads automatically as soon as you pick a file.

2. Run Optimize (compress)

Choose Document → Optimize (compress). The editor re-writes the whole file from its document model:

drops unused objects — orphaned data that viewers never reference (old revisions, leftovers from previous editors),
Flate-compresses streams that were stored uncompressed or poorly compressed,
deduplicates byte-identical streams, so repeated content is stored once.

3. Check the result

The optimised copy downloads as yourfile-optimized.pdf, and a message reports the change — for example "Optimized: 4.8 MB → 1.9 MB (−60%)". If the file was already compact, it tells you that too.

Lossless by design: this optimisation never re-encodes images or degrades anything — pages render pixel-for-pixel the same. That also means a PDF that is mostly large photographs may not shrink much; the big wins come from waste (unused objects, uncompressed streams, duplicates), which real-world PDFs carry surprisingly often.

4. Going further

If a document is still too heavy and you don't need selectable text, you can flatten pages to images at a chosen dpi (Export menu) — that's lossy, but can dramatically reduce scan-heavy files. Deleting unneeded pages first also helps — see Merge & split PDFs.

Tip: compressing locally means even huge files are processed at full speed — there is no upload to wait for, no daily quota, and no server seeing your document. See our Privacy Policy.

Compress a PDF now →

More guides: Merge & split PDFs · Edit a PDF · OCR a PDF