What you have to remember to make a good graphic for cover designs is that you have to make it bigger than you need. Leave edged all around. Even add edges if you can. In some cases you can’t. Then when you drop a graphic into a cover template, you have more room to work. Ideally, the template would be a little big so you can trim off part of the printed image for an clean edge (as opposed to trying to cut along an exact line and getting some white and then having to go back and recut and run the risk of an uneven edge). You have to plan for this when you place the images. The cover image may need to be a tiny bit offset. For professional printing they like to more room to cut. Though I just proofed something for work today that didn’t look like it had any over printing.
I’m just using the pdf provided here, is it high quality? I’m just going to print it at a print shop and have them cut it if they can.