Color isn't always welcome. Office printers charge more for it, some courts and publishers ask for grayscale submissions, and color scans of plain paperwork store far more data than they need. Grayscale PDF converts every page to shades of gray, so the document prints predictably on black-and-white printers and scanned color pages usually get smaller.
How to use Grayscale PDF
- Add the color PDF.
- Select Convert to Grayscale. There are no settings to choose.
- Download the grayscale PDF.
- Check charts and highlighted text, where colors that differ only in hue can look alike in gray.
Two ways the conversion runs
- With Ghostscript: On a server with Ghostscript, the document is rewritten with its colors converted to gray, which keeps text as real text and vector drawings as vectors, so the result stays sharp and searchable.
- Without Ghostscript, VelloDoc uses a fallback that renders each page as a grayscale image at 150 DPI.
- What the fallback costs: The fallback always produces a gray document, but its text becomes part of the page image and can no longer be selected or searched, so run OCR PDF afterwards if that matters to you.
When colors turn into the same gray
Grayscale keeps brightness and discards hue.
- Similar brightness collapses: A red line and a green line of similar brightness can become exactly the same gray, which matters for charts, color-coded tables and highlighted passages.
- Check before converting: Before converting a document where color carries meaning, check that the key elements still stand apart.
- Use labels and patterns: Where they don't, labels, patterns or line styles in the source document are more dependable than color alone.
Grayscale and file size
- Scanned documents: In scanned documents, color accounts for a large share of the data, so grayscale conversion often makes them noticeably smaller.
- Text-based PDFs change little, because text takes almost no space either way.
- Pair it with compression: When the goal is a smaller file, pair this tool with Compress PDF. The guide to reducing PDF size explains why.
- Where to read more: For print preparation more broadly, the print-ready PDF guide covers margins, flattening and booklets.
When people use Grayscale PDF
Saving on color printing
Convert handouts and reports before printing so a shared office printer uses only black toner.
Grayscale submission rules
Meet the requirements of courts, journals or agencies that accept documents only in black, white and gray.
Lighter scanned paperwork
Shrink color scans of forms and letters where the color adds nothing but megabytes.
Limitations to know
Grayscale PDF converts every page and can't keep selected pages in color. Colors of similar brightness can merge into the same gray. Without Ghostscript on the server, pages are rendered as 150 DPI images, which leaves text unselectable until OCR is applied.
Grayscale PDF: common questions
Will grayscale conversion make my PDF smaller?
Scanned and photo-heavy documents usually shrink, because color images hold more data than gray ones. Documents made mostly of text change very little.
Can I convert only some pages to grayscale?
No, the whole document is converted. To keep some pages in color, split out the pages you want in gray with Split PDF, convert them, and join everything back together with Merge PDF.
Why can I no longer select text in the grayscale file?
That happens when the server doesn't have Ghostscript and the page-image fallback is used. Run OCR PDF to add a searchable text layer again.
Is grayscale the same as black and white?
No. Grayscale keeps the full range of grays, so photos and shading still look natural. Pure black and white with no gray tones is a different conversion that this tool doesn't perform.