really greyscale pdf

Question

I may miss something: I cannot produce really greyscale or monochrome pdf. If I create a very simple document, say Hello, with no or basic packages, article or book, and compile it with pdflatex (which I need to use for my project), the pdf appears as greyscale in Texmaker viewer, but not in Acrobat or Foxit readers. It is rich black (RGYK). I have another document, compiled by someone else with pdflatex or pdftex, which appears greyscale OK in Acrobat. It is the same even if I add \usepackage[greyscale]{xcolor}. I am working with Windows and usually compile with TexnicCenter (but TeXMaker does the same). Any idea ?

MWE:

\documentclass[a4paper]{article}
\usepackage[monochrome]{xcolor}   

\begin{document}  
Hello    
\end{document}

Answer 1

I don't understand your problem: Here's a version of your MWE that I modified to produce an uncompressed PDF without any fonts embedded (just to make it easier to look at the PDF in a text viewer/editor, it won't affect the colour spaces):

\documentclass[a4paper]{article}
\usepackage{mathptmx} % use times font
\pdfcompresslevel=0   % don't compress the PDF
\pdfmapline{ptmr8r Times-Roman <8r.enc} % don't embed times font
\usepackage[monochrome]{xcolor}

\begin{document}
Hello
\end{document}

If you look at the resulting PDF (eg open it in a text editor) you can see that the text is produced by the following:

stream
0 g 0 G
BT
/F16 9.9626 Tf 139.746 706.129 Td [(Hello)]TJ 154.421 -615.691 Td [(1)]TJ
ET
endstream

The part 0 g 0 G sets the text to /DeviceGray black: this is a pure black, not a rich black. Changing to \usepackage[cmyk]{xcolor} the corresponding code becomes 0 0 0 1 k 0 0 0 1 K which corresponds to a /DeviceCMYK pure black (CMY components are all zero), so still not a rich black.

Adobe acrobat pro preflight and output preview tools agree with me that these options give /DeviceGray black and /DeviceCMYK non-rich black respectively.

So, I think everything is OK with this MWE. Please check with your full document if there is really a problem, and update the MWE to demonstrate it if so.