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How to make a PDF smaller for email and uploads
Shrink scanned and image-heavy PDFs without losing readability
Why PDFs get big
A PDF made from typed text is usually tiny. Size balloons when pages are photographs or scans, because each page is stored as a high-resolution image. A ten-page scanned form can easily reach 30 MB, which many email providers and government portals reject.
How FirePDF compresses
The Compress PDF tool redraws every page as an image at a lower resolution and JPEG quality, then rebuilds the document at the original page size. This is the same approach most online compressors use. It is very effective on scans and photos. It is not useful for text-based PDFs: the text becomes part of the picture and can no longer be selected or searched.
If the result would be larger than your original, the tool keeps your original file and tells you so, so you never get a bigger file by accident.
Choosing a level
- Light keeps the most detail. Choose it for documents with small print or fine drawings.
- Recommended is a balance for typical scans and forms.
- Extreme gives the smallest file. Text stays readable on screen but may look soft when zoomed in or printed.
Tips
- Compress last. Merge, rotate and edit first, because compressed pages cannot be edited as text.
- Keep your original. Compression is not reversible.
- If you need the text to stay selectable, try scanning at a lower resolution instead, or split the file into parts.
- Check the file before sending it. Open the compressed PDF and make sure numbers, stamps and signatures are still legible.
Everything described here runs inside your browser tab. Your files are not uploaded to a server, which you can confirm by turning off your internet connection after the page has loaded and running the tool again.
More help: all FirePDF guides.