Practical guide
PDF compression: file size versus quality
A smaller PDF is useful only when the text, diagrams and photographs remain clear enough for the document's purpose.
Published and reviewed
Why PDF files become large
Scanned pages and full-resolution photographs usually contribute most of the size. Embedded fonts, duplicate resources, attachments and complex graphics can also matter.
A text-based PDF may already be compact, while a scan of the same number of pages can contain millions of pixels.
How FileSwift compression works
The current FileSwift compressor renders each page and rebuilds it from optimized JPEG images. That approach can reduce image-heavy files, but it also changes document behavior because text, links and form controls can become part of the page image.
Choosing a setting
Start around 70–80% for ordinary scans. Use a higher value for small text, engineering drawings or screenshots. Use a lower value only when size matters more than fine detail.
Always compare the original and output at 100% zoom and print a test page when the document is intended for paper distribution.
When not to rasterize
Avoid this method when searchable text, accessibility, interactive forms, digital signatures or vector clarity must remain intact. A specialized optimizer may be more appropriate for those requirements.