Compress PDF

Why PDF Files Are Larger Than Expected

Many users are surprised by how large PDF files can be, especially when the source document didn't seem complex. Here are the most common culprits:

• Embedded images at print resolution — When you export from Word or PowerPoint, images are often embedded at 300 DPI (print quality). For screen viewing, 72–150 DPI is perfectly readable and far smaller.
• Scanned documents — Each scanned page is stored as a raw, uncompressed image inside the PDF container.
• Embedded fonts — PDFs embed entire font files to ensure consistent rendering across devices.
• Metadata and revision history — Documents edited many times accumulate hidden metadata and document history.

How Compression Works

Flixfer's compression engine applies several techniques simultaneously:

1. Image downsampling — Reduces embedded image resolution from 300 DPI to a screen-optimised 96–150 DPI.
2. Re-encoding — Switches image encoding to more efficient algorithms (JPEG for photos, PNG for diagrams).
3. Metadata stripping — Removes revision history, author metadata, and other non-essential data.

Compression Tips for Best Results

• For maximum size reduction on image-heavy PDFs, compress images before embedding them in your source document using Flixfer's Image Compressor.
• After compressing, verify the output by opening it at 100% zoom — if it looks fine on screen, it will be fine for most use cases.
• If you need to further reduce size, use Split PDF to separate large documents and compress each section individually.