How to Compress PDF Files to Reduce File Size

Why Compress PDFs?

Large PDF files can be problematic for several reasons:

• Email attachments — Most email providers limit attachments to 25MB
• Cloud storage — Compressed files save storage space
• Faster sharing — Smaller files upload and download faster
• Web publishing — Optimize PDFs for faster page loads

How PDF Compression Works

PDF Worker compresses files by re-rendering each page as an optimized JPEG image at a lower resolution, then reassembling them into a new PDF. This is highly effective at reducing file size, especially for image-heavy documents.

Trade-offs to be aware of:

• Text in the output becomes image-based, so it is no longer selectable or searchable
• Higher compression levels reduce both JPEG quality and DPI, producing smaller but lower-fidelity pages

For documents where text selectability is critical, consider using a low compression level or keeping the original alongside the compressed version.

Compression Levels Explained

Level	JPEG Quality	Resolution	Best For
Low	85%	150 DPI	Archiving — minimal visible quality loss
Medium	60%	120 DPI	General sharing — good size/quality balance
High	35%	96 DPI	Email, quick previews — maximum size reduction
Custom	You choose	120 DPI	Fine-tuned control over output quality

Tips for Best Results

• Start with Low or Medium — Review the output before going higher
• Always check the output — Verify text readability and image clarity
• Use High for quick previews — When file size matters more than fidelity
• Keep the original — Compression is lossy, so save your source file

Compress Your PDFs Now

Try PDF Worker's free PDF compressor. It works entirely in your browser — your files never leave your device. Choose from preset levels or set custom quality for precise control.