Grayscale troubleshooting: password errors, lost text, bigger files, and colour that stays

Grayscale runs entirely in your browser — your PDF is never uploaded — so most problems come down to the file itself or to the way the conversion works (pages are re-rendered as grayscale images). Here are the common ones and how to fix them.

"This PDF is password-protected, so it can't be opened to convert"

Cause: The PDF requires a password just to open it, so the converter can't read its pages. The error message links to the fix as "Remove the password first".

1. Open Unlock and enter the PDF's password to produce an unlocked copy. This also happens locally — the password and file stay on your device.
2. Bring the unlocked copy back to Grayscale and run it again.

Text isn't selectable or searchable after converting

Cause: This is by design, not a bug. A PDF's vector content can't be honestly recoloured in the browser, so Grayscale re-renders each page as a grayscale image — the result screen shows an amber notice about exactly this. The pages now contain pictures of text, not real text.

1. If you need selectable text back, run the converted file through Searchable (OCR) — the notice on the result screen links there. OCR adds a text layer so the document is selectable and searchable again.
2. Keep your original colour PDF too; OCR-recovered text is a recognition of the page image, not the original text, so spot-check anything critical.
3. If selectable text matters more than black & white pages, reconsider whether you need the conversion at all — for one-off printing, your printer's own "print in grayscale" setting saves ink without touching the file.

The grayscale file is bigger than the original

Cause: Pages are re-rendered as JPEG images at roughly 144 DPI. For scans and image-heavy files that's usually fine, but a compact text-only PDF stores text very efficiently — turning its pages into images can genuinely grow the file.

1. If you only need black & white for a single print job, skip the conversion and use your printer driver's grayscale option instead.
2. If you need a smaller black & white file to share, run the grayscale output through Compress — its "Make it smaller (flatten)" mode re-renders the (already grayscale) pages at a lower resolution.
3. For very long documents, consider splitting with Pages and converting only the parts you'll print.

Pages look blurry or pixelated when zoomed in

Cause: Rendering happens at about 144 DPI, and very large pages are scaled so their longest edge stays under 2600 px (this keeps the conversion inside browser canvas limits, especially on Safari and iOS). That's comfortably sharp for normal printing, but it's a fixed resolution — zooming far in on screen will show pixels, and oversized pages (posters, large-format plans) are downscaled more.

1. For standard letter/A4 documents headed to a printer, the output prints cleanly — judge it on paper, not at 400% zoom.
2. For large-format pages where detail matters, keep the colour original for viewing and use the grayscale copy only for draft printing.

The output is still in colour

Cause: Very old browsers don't support the canvas filter used to desaturate pages. In that case the tool deliberately falls back to a plain copy — you get a working PDF that stays colour — rather than failing outright.

1. Update your browser, or retry in a current version of Chrome, Firefox, Safari, or Edge. All modern browsers support the conversion.

Converting a large file is slow, or the tab feels stuck

Cause: All the work happens on your device — each page is rendered, desaturated, and re-embedded one at a time in your browser rather than on a server. Long or image-heavy documents are the heaviest case.

1. Wait for the Converting… button to finish — progress is normal even if the page looks quiet.
2. Close other heavy tabs to free memory, especially on phones and low-RAM machines.
3. For very long documents, split them first with Pages and convert the parts separately.

"Couldn't convert this PDF — it may be corrupted or in an unsupported format"

Cause: The file couldn't be parsed as a usable PDF. It may be damaged, truncated by a bad download or email transfer, or not really a PDF (e.g. a renamed image or Word file).

1. Confirm the file opens in another PDF viewer. If it doesn't open anywhere, re-download or re-export it from the source.
2. If it's actually an image, convert it to a PDF first with JPG to PDF, then run Grayscale on the result.
3. If the file opens fine elsewhere but still fails here, report it — that's a case the team wants to see.

Still stuck?

If none of these match what you're seeing, contact support and describe what happened — since your file never leaves your browser, support can't see it, so include the file's size, page count, and roughly what's on the pages.