I would check and verify:
1, paper size(double check units, if by custom);
2, layer attitudes(scratch layers won't be printed);
3, line type, width and color. Can you change and move to a new layer.
If still no luck, can you upload a minimum dxf example?
RobertRead wrote
In drawing an residential electrical plan, I created my own symbols for receptacles, lights, and switches by creating blocks. I could them move the blocks and duplicate as needed. After placing the blocks/symbols on the drawing and saving. I did print preview and only the lines and text in the drawings appears, none of the blocks/symbols appear. I tried exploding one block, modifying attributes, still does not appear in the print preview or a pdf. Any help would be appreciated.