Understanding PDF compression and choosing the right level
Large PDFs are usually large because of images: scanned pages, photos, or high-resolution graphics. Email services often cap attachments at 20–25 MB and upload forms frequently accept far less, so reducing file size is one of the most common PDF tasks.
How this compressor works
Each page is rendered and saved again as an optimized JPEG image, then the images are assembled into a new PDF. This is very effective for scanned documents and image-heavy files, which often shrink to a fraction of their original size.
Because pages become images, text in the compressed file is no longer selectable or searchable, and small text can look softer at higher compression. For a contract or report that people need to search or copy from, keep the original and use Low compression, or compress only the scanned sections.
Choosing a level
Low keeps the most detail and suits documents with fine print or diagrams. Medium is the best balance for most scans and is the recommended default. High produces the smallest file and is appropriate for previews, drafts and photo-heavy documents where some softness is acceptable.
After compressing, the tool shows the new size. Open the downloaded file and zoom into the smallest text before sending it; if it is hard to read, run the original again at a lower level.
When compression helps little
Text-only PDFs exported from Word or Google Docs are already small. Rendering them as images can actually make them larger. If such a file is unexpectedly big, the cause is usually embedded fonts or a few large images, and splitting off unneeded pages may help more.
Tips for smaller files
- Delete blank or duplicate pages before compressing.
- Compress scanned documents; leave text-based documents uncompressed where possible.
- Keep the original file — compression cannot be reversed.