A PDF that is too big to email or upload is a common headache. The good news is that most oversized PDFs can be reduced substantially without anyone noticing a difference. The key is knowing what makes the file large.
What makes a PDF large
- Images and scans. Photographs and scanned pages usually account for most of a file’s size, especially when they were captured at high resolution or saved with little compression.
- Embedded fonts. PDFs carry the fonts they use. Complete font files, or the same font embedded several times after merging, add weight.
- Duplicated and leftover data. Repeated logos, unused objects and editing history can remain inside a file.
Text itself is tiny. A 100-page text-only report is often well under 1 MB.
Start with recommended compression
Open Compress PDF and try the Recommended level first. It recompresses images to a sensible quality, cleans up fonts and removes unused data, while keeping text selectable and links and forms working. Compare the original and new sizes that Qpdf shows, then open the result and zoom in on a scanned page or photo to check it.
If the file is still too large, try Stronger compression, which lowers image quality further. If the images matter — photographs, plans, medical images — try Higher quality instead and accept a larger file.
Aim for a target size
Upload portals often have a fixed limit. Enter it as the target size and Qpdf searches for the best quality that fits. Aim a little below the limit, and if the target cannot be reached, Qpdf tells you rather than producing an unreadable file.
When compression is not enough
- Remove pages you do not need with Delete PDF Pages — blank backs of scans and duplicate pages are common culprits.
- Convert colour scans to greyscale with PDF to Greyscale if colour is not needed.
- Split the document into parts with Split PDF when a portal accepts several files.
- Re-scan at a lower resolution. For text documents, 200–300 dpi is usually plenty.
Things to avoid
- Rasterizing text pages. Turning pages into images can shrink some scans, but it removes selectable, searchable text and can make the file larger. Qpdf leaves it off unless you choose it.
- Compressing signed documents. Any change to a digitally signed PDF invalidates the signature. Qpdf leaves signed files untouched by default; compress before signing instead.
- Compressing the only copy. Keep the original until you have checked the smaller version.