Open Your image in Photoshop

Make sure it is the right size, according to the paper format you want: <BR> - Go to Image > Image Size <BR> if you would like to change the dimensions, make sure the chain is locked in order to keep the proportions <BR> - Put the resolution to 300 dpi, then click 'ok'

Check that your image is in CMYK: - Go to Image > mode > CMYK

Go to Window > Channels Go to the hamburger on the top right corner of the Channels window Choose 'Split Channels'

Then it opens 4 windows, 1 for each channel: (Cyan, Magenta, Yellow and Black)

This you’ll have to do for each Channel: Go to Image > Mode > Bitmap It opens this little window Keep the input and output to 300 dpi. Choose the raster you like, most often Halftone Screen

You will have to put a different angle for each Channel Opinions differ on this, but here is one you can use: Frequency: 45 (for all) Angles: cyan 82 /magenta 52 /yellow 7 /black 22 Shape: Round or Ellipse (same one for all)

Check at 100% view if the dots looks right. (shortcut is cmd+1)

Now we are going to add cropmarks, necessary for a good alignment of the 4 layers :) Import each 4 .psd file into a Indesign file of the same dimensions. Then just save each file as PDF, and tick the option 'Add cropmarks' on the export panel of indesign, in 'Marks and bleeds'. Click 'Press quality' and 'Export'