How to compress PDFs online

PDF compression depends heavily on what is inside the document. A PDF made from typed text is usually easier to optimize than a scanned PDF filled with high-resolution images. That is why two PDFs with the same page count can produce very different compression results.

What makes a PDF large?

Large PDFs usually contain oversized photos, scanned pages, embedded fonts, duplicated resources, or hidden editing data. A safe compressor can rewrite the structure of the file and remove some overhead, but it may not dramatically shrink scanned pages unless it also changes image quality.

When should you compress a PDF?

• Before uploading to a form with a strict file-size limit.
• Before emailing a document to someone on a slow connection.
• Before storing many related documents in a shared folder.

How Compressly handles PDFs

Compressly currently performs browser-side PDF optimization. It loads the file locally, rewrites the PDF with object streams, and gives you an optimized copy. The file is not sent to a Compressly server for processing.

What to do if the PDF is still too large

If a PDF barely changes, it may already be optimized or it may be made mostly of scanned images. In that case, try exporting the original document at a lower image quality, splitting unrelated pages into separate files, or converting image-heavy pages before creating the PDF.

Ready to try it? Open the file compressor.