How to Compress a PDF Without Losing Quality

Large PDFs are a daily frustration — email providers reject attachments over 25 MB, WhatsApp blocks files over 100 MB, and government portals often cap uploads at 2 MB. Yet compressing a PDF the wrong way can make text blurry and images unreadable.

Here's the good news: you can significantly reduce PDF file size without visibly losing quality if you understand what makes PDFs large in the first place.

Why are PDFs large?

PDFs become bloated for a few reasons:

• High-resolution embedded images — scanned documents, photos, and screenshots at 300+ DPI are the single biggest contributor to file size.
• Embedded fonts — full font subsets can add hundreds of kilobytes.
• Metadata and revision history — PDFs that have been edited multiple times retain revision data.
• Uncompressed page streams — some generators don't apply stream compression.

The right way to compress

The most effective approach for most PDFs is to re-render each page as a compressed JPEG image. This is exactly what PDFTools does:

1. Each page is rendered using PDF.js at an appropriate DPI.

2. The rendered image is re-encoded as a JPEG at a quality level you choose (low, medium, high).

3. pdf-lib reassembles the images into a new PDF.

Pro tip: Use "Low compression" (85% JPEG quality) for documents where text sharpness is critical, like legal contracts. Use "High compression" (35% quality) for scanned images or photos where file size matters more.

When to use which setting

Try PDFTools Compress now — your files never leave your device.