Im having hassles with a document that is created in 100%K and with a greyscale bitmap, when I publish to pdf prepress native, the black is separated into four colours and the greyscale bitmap also turns into cmyk. When I import the pdf back into corel the colour is still correct 100%K and greyscale, but the printshop I send the document to as well as another reprohouse receives the file with black changed into four colours and the greyscale bitmap is turned into cmyk. I tested another document using pdf prepress cmyk and the repro house also received the document with the black changed into four colours cmyk. This is not the first time I have this problem, I had the same problem a year ago and since then have been using pdf x1a to publish my documents for printing. However, when publishing to pdf.X1a the greyscale bitmap becomes lighter and I understood from my printshop that pdf x1a is not a good type of pdf to use for printing?
Is there a solution for this?