Not an easy task in the case of PDFs, since they can contain several resources that each have their own color space. For instance, a CMYK PDF can contain bitmaps that use RGB or CIE color spaces. Simply removing the information is already hard enough, but making sure each conversion matches the overall setting is a challenge.

As for bitmaps, we prefer to leave image editing to specialized software. There are plenty of free and professional tools out there to convert bitmaps to grayscale, manually or in batch.

Still, I'll keep you suggestion on file because we've been known to change our minds from time to time! :-)
Technical Product Manager
I don't want to achieve immortality through my work; I want to achieve immortality through not dying - Woody Allen