How to compress a PDF (and why size varies so much)

Not all PDFs compress equally. Understanding why helps you get the smallest file without wrecking quality.

Why some PDFs barely shrink

A PDF that is mostly text and vector graphics is already compact — there's little to remove, so you might only save 10–20% (or none). A scanned or image-heavy PDF, on the other hand, can shrink by 80–90% because the images inside can be downsampled.

Compression levels

• Strong (≈72 dpi) — smallest file, best for email/screen.
• Balanced (≈150 dpi) — great size/quality trade-off.
• High quality (≈300 dpi) — print-ready, modest savings.

The golden rule

A good compressor never returns a bigger file — if compression can't help, you keep the original. Best Convert PDF applies a lossless structure pass first (qpdf), then image downsampling (Ghostscript), and only keeps the result if it's actually smaller.

Privacy

PDFs are processed on a secure server and deleted automatically right after — we never keep your documents.

Try it now — free

Drop your PDF into Best Convert PDF, pick a level (Balanced is best for most), and download the smaller file. Free and secure.

Open the free compressor →