FreePik has this really nice magazine PSD mockup, high-resolution and free to download. I like this one in particular because it’s straight-on, so you could use it to show off a 4-page newsletter just as easily as a 64-page magazine.

If you’ve never used Photoshop smart objects, just double-click the layer with the magazine art on it, drop your artwork into the resulting file and save it and boom… your magazine mockup is updated to show off you design.