Trapping Issues In Illustrator - overprinting not saving when printing

[eskopdl]

If you are doing any volume at all of trapping files in Adobe Illustrator, then you really should look at these solutions and tools.
EskoArtwork: Trapping made easy
Good luck - peter

[Lukas Engqvist]

Very few inkjet printers are printing overprint, since overprint is a function of postscript separation (or similar). The only way to show overprint is to simulate it, either by using a proofer rip in your workflow or by choosing to simulate overprint in Illustrator, or acrobat.