Guides / Converting scanned PDFs to grayscale for applications

Converting scanned PDFs to grayscale for applications

Many application portals are happy with black-and-white or grayscale copies of documents, and grayscale files are usually much smaller than colour ones.

Why people convert to grayscale

Colour scans store three channels of information per pixel; grayscale stores one. For documents that are mostly black text on white paper, converting often saves a large share of the file size while keeping the text readable.

When to be careful

• Check whether the portal or the requesting office asks for colour copies. Some do, for example for IDs, certificates with coloured seals, or photographs.
• Coloured stamps and highlights become shades of gray. Make sure they remain legible.

What FileMending converts

With the grayscale option on, colour images inside PDFs (the typical scan) and standalone JPG or PNG files are converted to grayscale. Coloured vector text or graphics in a PDF are not changed. Files that are digitally signed, password-protected, or marked quality-locked are left as they are and flagged, so a signature is never silently broken.

How to use it

1. Open FileMending and enter your limit.
2. Add your files and press Check.
3. Under Advanced settings, tick Convert to grayscale, then press Fit.
4. Review the before and after preview, zooming into small print.

Frequently asked questions

Is grayscale the same as black and white?

No. Grayscale keeps shades of gray, which preserves detail in text edges, stamps and photos. Pure black and white removes the shades and can make small print harder to read.

Will converting to grayscale make my PDF smaller?

Usually yes for colour scans, but the amount depends on the file. FileMending shows the exact before and after size.

Does it work on signed PDFs?

Signed or protected PDFs are left unchanged and flagged, because changing them could invalidate the signature.

Updated 2026-10-12. General information, not legal advice. Always check the requirements of the portal or office you are uploading to.