Using InDesign (Illustrator is pretty much the same):
1) Create a new layer and rename this ‘White’ with a capital ‘W’ (this is because of the print software – always use a capital W!). This layer will contain the white segments of your design.
2) Now you need to create a new colour swatch. Go to ribbon at the top of the screen select Window > Colour > Swatches. Ensure you are set to CMYK colour mode!
3) In the top right-hand corner of the Swatch Palette, select “Add New Colour.” Change the colour type to “spot” colour using the drop-down menu. Rename as ‘White’. It will default to black but change this to magenta. This will allow you to see the areas to print in white much better.
4) On the White layer, with the White colour, fill in the objects that you need colouring white. If the item you want white is behind a design element, you need to trace the shape you need.
5) To trace text, boxes or shapes, go to Window > Output > Attributes and tick the box for Overprint Fill and if applicable, Overprint Stroke.
6) For a CMYK image, select this and go to Object > Effects > Transparency and select ‘Multiply’. You should now see magenta (the representative colour for white) showing through the image.
7) Now you need to save your file. Make sure the white layer is at the top with the rest of the artwork behind it. Save as a PDF.
