Hi everyone,
I realize I'm a bit late to the conversation but I have realized that this only happens when you print the PDF. If you print straight from Vectorworks, the crop box does not show up. I had 3 pages I wanted to print as a set so I published them to PDF then printed from Adobe Acrobat, and the crop box printed. But when I printed the same document straight from Vectorworks, the crop box did not print.
Hope this helps!