How to Compress Images In PDF
Image-heavy PDFs from design files, photo reports, and scanned documents can balloon to hundreds of megabytes, making them impossible to email or slow to load online. Compressing the embedded images is the most effective way to shrink these files because images account for 90%+ of the file size. SublimePDF recompresses every image in your PDF to your chosen quality level while keeping text and vectors untouched.
Follow the step-by-step instructions below, then use the free tool directly — no registration or download required.
Open Tool →How to Compress Images In PDF — Step by Step
Upload your PDF
Open the Compress Images in PDF tool and upload your document. The tool scans the file and reports the number of embedded images, their current compression, and total image data size.
Select compression level
Choose Low (slight reduction, visually identical), Medium (good balance for business documents), or High (maximum compression for email/web). Each level shows an estimated output size.
Configure advanced options
Optionally set a maximum image resolution (e.g., 150 DPI for screen viewing, 300 DPI for print). Images above this threshold are downsampled, providing the biggest file size savings for scanned documents.
Process the PDF
Click 'Compress' and the tool recompresses each image individually, choosing optimal JPEG quality for photos and PNG compression for graphics. A progress bar shows each page being processed.
Compare and download
The results screen shows the original vs. compressed file size and percentage reduction. Preview any page to spot-check image quality before downloading.
Pro Tips
- 💡 For documents that will only be viewed on screen, 150 DPI and medium compression typically reduce file size by 60–80% with no visible quality loss.
- 💡 If your PDF contains a mix of photos and text, the tool handles them differently—photos get JPEG compression while line art and text stay crisp.
- 💡 Run compression after merging multiple PDFs, since each source document may have used different image settings.
- 💡 For archival documents where quality is paramount, use the Low compression preset—it still achieves 20–40% size reduction while preserving near-original image quality.
Privacy & Security
All processing happens directly in your browser. Your files are never uploaded to any server — they remain on your device throughout the entire process. SublimePDF uses WebAssembly technology for fast, secure, client-side processing.
Works Everywhere
This tool works on any modern browser — Chrome, Firefox, Safari, or Edge — on desktop, tablet, or mobile. No software to install. PDF is an open ISO standard supported by all major platforms.
How to Compress Images In PDF — FAQ
Does image compression affect text in the PDF?
How much smaller will my PDF be?
Can I compress a specific page's images only?
Is there a risk of making images too blurry?
Related Guides
How to Compress PDF for Email
Email services typically limit attachments to 25MB. If your PDF is too large, SublimePDF can compress it dramatically while maintaining readable quality — perfect for sending via Gmail, Outlook, or any email service.
How to Compress PDF On Mac
Large PDFs are a constant friction point on macOS — they clog email attachments, slow down Finder previews, and eat into your iCloud storage. macOS Preview has a built-in 'Reduce File Size' Quartz filter, but it aggressively downgrades image quality with no control over compression levels. SublimePDF gives you adjustable compression that lets you choose between maximum quality retention and smallest file size.
How to Compress PDF On iPhone
Oversized PDFs on your iPhone make it impossible to share files via iMessage, email, or AirDrop when you're away from your computer. iOS has no built-in PDF compression tool, so files from scanned documents, presentations, or image-heavy reports stay at their original bloated size. SublimePDF compresses PDFs directly in Safari on your iPhone so you can shrink files instantly and share them without delay.