You can mark the current topic for printing using Mark for Print on either the hotspot pop-up menu or the general document pop-up menu.
The document you mark for print will be added to the Marked Topics list in the Mark Topic for Printing dialog accessible through the File menu. You can print the topics in the Marked Topics list by selecting Print Marked Topics... from the File menu.
When you choose Mark This Topic For Printing in a pop-up menu, the current topic will be marked for printing, and added to the Marked Topics list in the Mark Topic for Printing dialog.
If you choose Mark "[document]" For Printing in a hotspot popup menu for a hotspot in the index pane that links to a document (for example, a graphic), the linked topic will be added to the Marked Topics list. The popup menu for thumbnail images in the index pane will also allow graphics to be marked for printing.
You can view and edit the current Marked Topics list in the Mark Topic for Printing dialog by choosing File | Mark Topic for Printing....