Compress PDF

1. Upload a PDF file by dragging and dropping or clicking to browse.
2. Click "Compress PDF" to optimize the file.
3. Review the original and compressed file sizes.
4. Download the compressed PDF.

What is PDF Compression?

PDF compression reduces the file size of a PDF document to make it easier to share, upload, or store. PDF files can grow large due to embedded fonts, high-resolution images, redundant data objects, and metadata accumulated from multiple edits. This tool performs structural optimization by loading the PDF and re-saving it, which strips unused objects, removes redundant data, and re-structures the internal file layout. All processing runs entirely in your browser, so your documents remain private.

How Browser-Based Compression Works

This tool uses the pdf-lib JavaScript library to parse the PDF, traverse its internal object tree, and rebuild the file. During this process, unused objects (such as deleted pages, old revision data, or orphaned resources) are discarded. Cross-reference tables are rebuilt efficiently, and the output uses optimized serialization. This approach does not re-compress embedded images or fonts, which would require computationally intensive server-side processing. For PDFs with bloated metadata or many revisions, the savings can be significant. For image-heavy PDFs, the reduction may be modest.

Common Use Cases

• Reducing PDF size for email attachments (many providers limit to 25 MB)
• Optimizing PDFs before uploading to web forms or CMS platforms
• Shrinking files for cloud storage to save space and bandwidth
• Preparing documents for archival with minimal file size
• Cleaning up PDFs that have grown large after multiple edits

Why PDF Files Get Large

PDFs accumulate size from several sources. Embedded images are the most common culprit, especially when photos are included at full DSLR resolution. Embedded fonts add several hundred KB each, and some tools embed entire font families even when only a few characters are used. Incremental saves in editors like Adobe Acrobat append changes without removing old data, causing the file to grow with each save. Scanned documents often include high-resolution raster images. For maximum compression of image-heavy PDFs, consider reducing image resolution or converting to more efficient formats before embedding.

For other PDF operations, try Merge PDF, Split PDF, or Add Page Numbers. To convert PDFs, see PDF to Image or PDF to Text.