- I have a picture, on that picture I draw 10 boxes with each a different overprint color. (using CMYK based colors)
- Then a PDF v1.3 is created. On the preview (in Acrobat 9) all boxes are correctly visualized as overprint.
- When printed on an AGFA Sherpa the result is correct, all boxes are outputted overprint.
- When outputting this PDF onto 4 plates (CMYK) through an AGFA rip (for newspapers) the result becomes knockout for all boxes.
When they upgrade to produce PDF´s in version 1.4/1.6 should it be possible to output all boxes correctly overprint on 4 CMYK plates?
What are the alternatives in case this upgrade is not possible? Reprint the v1.3 through distiller to create a higher PDF version?
When a color is used containing both Black and Cyan, the visualisation and output in Adobe will become knockout for this color. Should it be possible to use an ovreprint color using Black and Cyan and still print as overprint on 4 CMYK plates? Or only in the newer PDF versions?
There are a few issues at play in your question. Primarily, though, the answer is based on your PDF version. Transparency/overprint/knockout features have changed in the last few versions of the PDF specification. For example, the text knockout parameter was added in PDF 1.4, and includes a flag to specify what elements are affected.
Prior to PDF 1.4, you couldn’t specify the feature. So the overprint parameter in the file would be false by default. As a result, your overprint color causes the underlying color to be erased, and you have a knockout.
Unfortunately, redistilling the file at a higher PDF version won’t make a difference unless your output device uses a newer or higher PDF version. The overprinting/knockout effect is device-dependent and not defined by the PDF language.
For reference, here’s an online location where you can read the PDF 1.7 Reference:
http://www.verypdf.com/document/pdf-format-reference/index.htm (click BOOKMARK at the top of the page to view the table of contents)
donna.
A prolific author and writer of many Acrobat books, as well as books on graphic and Web design software.
Donna lives on a lakeshore in central Canada, where all manner of wildlife from muskrats to coyotes come to call.