How to Compress a PDF File Online
Reduce PDF file size dramatically with our free PDF Compressor. Choose compression level to balance file size and quality for email, web, or print.
Steps
Upload your PDF
Upload the PDF you want to compress. The tool accepts any PDF regardless of content type: scanned documents, graphics-heavy reports, forms, and text documents all benefit from compression.
Choose compression level
Select the compression level: Maximum compression (smallest file, some quality loss — good for archiving older documents or scans), Medium (balanced file size and quality — best for email and web), Low (minimal quality loss — good for documents that need to remain printable at high quality).
Compress and review
Click Compress. The tool processes the PDF, applying image re-compression, removing redundant data, and optimising the file structure. The result shows original size, compressed size, and percentage reduction.
Download the compressed PDF
Download the compressed PDF. Open it to verify the quality meets your requirements. For most text-heavy PDFs, even maximum compression produces visually identical results because text is stored as vectors, not as images.
Why PDF Files Become Large
PDFs become large for several reasons. Embedded high-resolution images: scanned documents and reports with photographs contain large image data — a 300 DPI scan of an A4 page is several megabytes before compression. Embedded fonts: PDFs can embed full font files to ensure correct rendering on any device, but embedding multiple fonts adds to file size. Layers and hidden data: PDFs created from design applications like InDesign or Illustrator may contain hidden layers, editing data, and comments that are invisible in the final document but add file size. Version history: iteratively edited PDFs accumulate old versions of pages. Unoptimised image compression: many PDF export settings use low compression by default. PDF compression tools address all of these systematically.
Frequently Asked Questions
Compression potential depends heavily on the PDF's content. PDFs with many high-resolution photographs (scanned documents, photo books) can be compressed by 50–90% with moderate quality loss. PDFs containing mostly text and vector graphics compress only 5–20% because text is already efficiently stored. PDFs created by a scanner at high resolution and already-compressed images show little further compressibility.