PDF Compression

How to Compress a PDF Online

Last updated · By the PDFSolution team

Most oversized PDFs are oversized for one reason: they contain scanned or photographic pages stored at far more resolution than anyone will ever look at. A ten-page text document is rarely a problem; a ten-page scan from a multifunction printer easily runs to 40 MB.

Compression works by re-encoding those page images at a lower quality. That is a trade: you give up some sharpness to gain a smaller file. The trick is deciding how much you can afford to give up.

Ready to do it now? Open the tool this guide describes.

Compress PDF

Step by step

  1. 1

    Open the compressor and add your file

    Drop the PDF onto the Compress PDF page. The file is read by your browser; nothing is uploaded to a server.

  2. 2

    Pick a compression level

    Start with Recommended. Use Less compression when the document contains fine print or detailed drawings, and Strong when the only goal is to get under a size limit.

  3. 3

    Compress and compare

    The tool reports the size before and after so you can judge whether the saving is worth it before downloading anything.

  4. 4

    Download and check a detail page

    Open the result and zoom into the smallest text on the busiest page. If it is still legible, you chose the right level.

Useful tips

  • If a document is only large because it contains several files stitched together, deleting unnecessary pages first often saves more than compression does.
  • Scanning in greyscale rather than colour, at 300 DPI rather than 600, prevents the problem at source.
  • Compression rebuilds pages as images, so selectable text is lost. If you need searchable text afterwards, run OCR on the compressed file.

Common problems

The file barely got smaller
That usually means the PDF is mostly vector text, which is already compact. There simply is not much to squeeze out.
The text looks fuzzy
Step down a level and compress the original again — repeatedly compressing an already-compressed file makes quality worse without saving much.
The browser ran out of memory
Very large documents can exhaust a mobile browser. Split the PDF into parts, compress each, then merge them again.

Frequently asked questions

How small can a PDF get?
There is no universal figure. Image-heavy scans often shrink by 60-90%; a text-only PDF may shrink by almost nothing.
Does compressing lose quality?
Yes, some. The stronger the level, the more visible the softening, especially on small text and thin lines.
Is compression reversible?
No. Keep the original file if you may need the full-quality version later.
Is my file uploaded?
No. Compression runs in your browser on your own device.

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