Update README.md to clarify Poppler grayscale warning message (#662)

diff --git a/README.md b/README.md
index ce521bcb0edd55024c7fad817a0645ee155c6543..d4adf8e457894da59611a273c822f7b198049189 100644 (file)
--- a/README.md
+++ b/README.md
@@ -174,6 +174,12 @@ DeviceRGB, DeviceGray, RGB or sGray and is not capable of
 generating PostScript level 1. So its support is only experimental
 and distributions should not choose it as default.
 
 generating PostScript level 1. So its support is only experimental
 and distributions should not choose it as default.
 

+Poppler does not explicitly support turning colored PDF files into
+grayscale PostScript, that's why grayscale/monochrome printing
+could result in color output.  
+Use alternative backends, such as Ghostscript or MuPDF, if this is
+the case with your printer.
+

 The selection is done by the "pdftops-renderer" option, setting it
 to "gs", "pdftops", "pdftocairo", "acroread", "mupdf", or "hybrid":
 
 The selection is done by the "pdftops-renderer" option, setting it
 to "gs", "pdftops", "pdftocairo", "acroread", "mupdf", or "hybrid":