Grayscale conversion isn't available yet

We've taken this tool offline. An earlier version re-saved your document without converting anything to black and white, while reporting that it had worked.

Converting a PDF to true grayscale means re-processing every image and colour instruction in the file. We'd rather ship that properly than return a colour document and call it done.

If you're printing: nearly every printer dialog has a "Black and white" or "Grayscale" option, which achieves the same result without changing your file at all.