I can add sketched lines, but is that going to make the invisible hash marks visible? (They're invisible because Solidworks only wants to show the stuff that will "print" on the part.) I can already see the edges of the part, which is what the hash marks line up with. It's the hash marks that don't show. Perhaps there's an option to make them visible, temporarily.
The hash marks are correctly placed. They're not especially pretty, so the custom for this type of artwork is to have them off the edge of the label you're making, but indicating how it lines up with the edges. When I say "decal", I mean the Solidworks decal function. This is an overlay that is then applied to a part. We want it to look right in the assembly.
I suppose I could ask for artwork with extra lines on it in places that will be cut off and punched out. Then, if I can't see the lines, it must be in the right place. But that's a mess and another pass, and is not customary.