I’ve tried putting everything in one large artboard and printing that large artboard, but it would not show the trim marks for the smaller artboards.
To place trim marks around artboards
Select File → Save As (Ctrl+Shift+S) and select PDF
Once the PDF options come up, click on Marks and Bleeds and check Trim Marks
To place crop marks around individual objects
Select all items you want and go to Effect → Crop Marks this will apply crop marks (trim marks) to each object.
See this answer for more.