I would remove the trim marks with the Optimize node. I am going to make the assumption that your pdfs have media box = crop box = bleed box = trim box = art box. I would setup 2 Resize nodes in series. The first Resize node uniformly increases all the pdf boxes by 2mm. The second Resize node decreases the trim box by 2mm (so that it has its original size).
This is for a business card workflow
Im looking to find a way to remove print marks (i Know i can do this with the optimise node) and then add 2mm bleed to the document, could someone describe the best way to do this, the file would always have a trim box in place