Converting to Grayscale - Crop marks

[Peter_Steeper@adobeforums.com]

I have a PDF that has colour and BW pages. There are crop marks on each page that are 100% CMYK including the BW pages. I need to convert the BW pages to remove any colour info to avoid colour click charges.

I tried converting the BW pages with Convert Colors using 15% Dot Gain. This converted the content of pages but not the crop marks. I tried the various conversion options. Embed Profile as Output converted the crop marks but it also converted the colour pages even when I selected a page range.

How do I get the crop marks to convert?

I am using Acrobat Pro 8.1.2.

Thanks

[Jon Bessant]

Make sure you have DON'T EMBED PROFILE selected (also select PRESERVE
BLACK OBJECTS) - this will indeed convert the colour space of all objects?

If you want to remove the crop marks (and providing they're outside the
trim box) then why not use the preflight fixup called 'Remove objects
outside page area' and select TRIMBOX. It's worth changing your Acrobat
view preferences to reflect this via Preferences / Page Display /
Display art, trim and bleed boxes (switch ON).

Cheers,

Jon