Large PDFs are hard to email and slow to upload. Most PDFs are big for one reason, and you can usually shrink them without making text blurry once you know what to look for.
Why PDFs get so large
Text is tiny. A 20-page text document is often well under 1 MB. The size comes from images – scanned pages, photos and screenshots – and from embedded fonts. A scan at 600 DPI can weigh several megabytes per page, far more than a screen or normal printer needs.
Step by step
- Check what is inside. If the pages are scans, images are your target. If it is exported text, size is rarely the problem.
- Lower image resolution sensibly. 150 DPI is fine for reading on screen. Use 200–300 DPI if the file will be printed.
- Use stronger compression for photos and gentler settings for text-heavy scans so letters stay crisp.
- Remove what you do not need – unused pages, attachments and extra metadata.
- Compare before sending. Zoom to 100% and read a few lines and any small print. If it is hard to read, raise the quality a notch.
Quick size targets
- Email: under 10 MB is safest; many providers limit attachments to around 20–25 MB.
- Online forms: check the stated limit – many ask for 1–2 MB.
- Printing: keep higher quality; size matters less.
Common mistakes
- Compressing the same file again and again, which adds visible artefacts. Always compress from the original.
- Using the smallest setting on documents with signatures or stamps.
- Not keeping an untouched copy.