You can display and plot a border around the PDF underlay or the clipping boundary.
A frame is a visual border that shows the extents of the underlay, or the clipped boundary of the underlay. When underlay frames are hidden, clipped underlays are still displayed to their specified boundary limits; only the boundary is affected.
Use the PDFFRAME or FRAME system variables to not only display frames, but also to specify whether or not to plot them.
Note: Underlays can be selected if they are not on a locked layer; for example, if the underlay is part of a named selection set made with the All option when selecting objects.
The following foreground example shows the underlay with a visible frame:
The foreground example shows the underlay with a visible frame.