Compress PDF Online Free

Reducing the size of a PDF shouldn't require uploading your private documents to a stranger's server. SigPDF's free PDF compressor runs entirely in your browser — your file never leaves your device.

The tool works by re-serializing the PDF document, which removes unused internal objects, duplicate data streams, and metadata that accumulates as PDFs are created and edited. This is a lossless process: your pages, text, images, and formatting remain completely unchanged.

What Gets Removed

• Metadata — title, author, subject, keywords, producer, and creator fields are cleared
• Unused objects — deleted pages, orphaned fonts, and unreferenced resources left behind during editing
• Duplicate streams — redundant copies of the same data that inflate file size
• Cross-reference bloat — re-serialization rebuilds the PDF's internal index from scratch

When to Expect Good Results

PDFs that have been edited multiple times, merged from several sources, or exported from tools that embed extra data tend to see the best results (10-40% reduction is common). PDFs that are already clean and mostly compressed images may see little to no reduction — the tool will tell you honestly if that's the case.

Common Reasons to Compress a PDF

• Attaching to emails — many email providers limit attachments to 10-25 MB
• Uploading to web forms — application portals, government websites, and job boards often have strict size limits
• Sharing via messaging apps — smaller files send and download faster
• Saving storage space — batch-compressing archived PDFs can free up significant disk space
• Faster loading — smaller PDFs open more quickly in browsers and PDF readers