I am exporting a PDF/X-1a file from Scribus 1.4.6 on Fedora 26.
I have converted all the colors in the image to CMYK, and have selected the profile my printer requires (CoatedGracol2006). When I export to PDF, the colorspace in the output is always sRGB (verified by using the ImageMagic `identify` command).
Oddly, if I use the Pre-Press option to add Crop Marks, Bleed Marks, or Registration Marks, then the output PDF is in the CMYK color space. However, my printer does not want these marks. How can I output CMYK without the marks?
I have attached the file using the Collect option (update: collect did not work, the file sizes are too large -- I attached the scribus file and we can go from there if other stuff is needed).