I duplicate files all of the time. Most of the time, it's because I need another version of the same thing; for example, I keep time sheets on a lot of my clients, and when I need a new one, I duplicate an old sheet and just edit it with the new info rather than reinventing the wheel every time.
If you'd like to do this for your files, too, there are only about 47 ways you could do so, without us even going into how to use the Terminal or anything fancy like that. So let's take a look at several ways to duplicate files in macOS.
The first and often best method for duplicating files is to use the Finder. Locate and select the file or files you'd like to duplicate and then choose File > Duplicate from the menu bar at the top of the screen.
Alternatively, you can select your file(s) and then use the keyboard shortcut Command-D. There's also a duplicate command in the right-click contextual menu. Just select your files, right-click (or Control-click) on them, and select Duplicate from the menu.
Yet another way to access the duplicate files command is via Finder's "Action" menu, which looks like a little gear in the Finder toolbar. With your desired files selected, click the Action Menu icon and select Duplicate.
If you're not satisfied with the multiple Finder menus that offer the duplicate files command, there's another option (get it?) and it happens to be my favorite. Just select your desired files, hold down the Alt/Option key on your keyboard, and then click and drag on the files. Instead of moving the files, a copy of the files will be placed in the location where you drop them.
You can tell that you're copying (or duplicating) your selected files by the presence of a green plus icon next to your cursor. You could use this Option trick to drag a file from your Documents folder to your Desktop, for example, which will leave the existing item within Documents and create a copy on your Desktop. Neat!
If you create duplicate files in a new location, you'll simply receive a new copy with the same file name. But if you create duplicate files in the same folder, your new duplicated copies will have a number appended to the end of the file name since you can't have two files with the same name in the same directory.
Oh goodness, that doesn't mean I have twice as much work to do now, does it? I don't think so, but I'm going to put that copy into the trash just to be sure.