I just tried this real basically, but it worked. I designed my ad in designer pro, letter size landscape. Exported to pdf, looks perfect on screen. Print it with the fit option,uneven margins/whitespace. On an inkjet you can make it print perfectly if you have the edge to edge option, but lasers don't print edge to edge. I had to send it to a business to print on a laser. There are several options when you go to print but doesn't make it print centered. I tried the bleed margin option in xara and re-exported. I used a significant margin of .20 inch. I need to experiment more but fixed it for today! Tried to upload pdf examples to attach - didn't work.