There are two symbols-sequences: "3-D" and "printer". You need the bold word indicator in front of each of these sequences. Only a space or terminator stops the bold word effect, so, yes, you need a bold terminator after "printer".
Standing alone has to do with contraction usage, not typeforms. With typeforms, you are focusing on symbols-sequences. For instance, "in" in "father-in-law" is standing alone because there is a dash on either side of it. You can use the contraction for "in". The entire compound word, however, only needs one italic word indicator in front of it if the whole thing is italicized. If only "in" were italicized, then you would need the italic terminator after "in" to prevent "law" from also being italicized.