What Is a PCB Designer Anyway?
A PCB is a Printed Circuit Board. The picture below is a photograph of a simple PCB after it has been manufactured at a "board house." This PCB is called a "bare board"—it does not not have any electrical components mounted on it as yet. A printed circuit board in this preliminary form is more properly called a "printed wiring board," because it doesn't actually have circuits and won't until components are soldered onto it. What it does have is a set of copper traces called "wiring," that have been applied by a process loosely analogous to printing.
Adapter board - top
Here is another example of one: Have you ever looked inside your computer, a radio or a telephone? The printed circuit boards inside it are the flat, thin, square, usually green fiberglass slabs that have electrical components attached. Harder to see are copper traces running underneath the green covering. You would have to try different angles of light to see them. These are wires that are "printed" on the fiberglass slab. They connect the electrical components, thus forming circuits. Thus the name "printed circuit board."
A company that manufactures electronic products has a cycle of production to go from concept to end user or customer. It could be thought of like this: Marketing - Sales - Product Concept - Engineering & Design - Design for Manufacturing (the portion done by a PCB designer) - Manufacturing - Assembly - Packaging - Distribution.
And now what is a PCB designer ?
The Design for Manufacturing step is where a PCB designer (slang: "layout guy" or "layout gal") makes his contribution to that portion of the product that involves electronic circuits. For that part of the product, an electrical engineer has done the engineering, or circuit design in the step just before this. He has produced, among other sub-products, a diagram of the functionality of the circuit. This diagram is called a "schematic." It contains symbols connected by lines. For example, a zig-zag line is used to represent a resistor, a type of electrical component that reduces the voltage of a current that passes through it.
The little zig-zag line does not even resemble what a resistor looks like, it simply symbolizes the function of a resistor, that it sort of "slows down" or impedes the current. (It reduces the voltage--the potential energy-- of the current.) A schematic diagram is composed of a variety of such symbols, not one of which looks like the physical component which it represents. Here is a physical representation of the resistor in 3D (from our PCB design software, Altium Designer).
So here you have an illustration of the concepts: The schematic symbol represents the function of the part and the PCB represents its physical characteristics (size, shape, electrical terminals as metallized objects, name as text and location).
In order to manufacture a printed circuit board, it is necessary to take the design from the functional diagram or schematic and change it into a form of artwork that makes a pattern of components, holes and wires. This pattern is nowadays in the form of digital data and is used by a bare printed circuit board manufacturer (slang: "board house") to control their photographic imaging techniques and computer-controlled drilling machinery, all resulting in the manufacture the PCB. The PCB designer is the person who creates the artwork for that purpose. The artwork is a lot like the plates used in printing, it forms the pattern that is "printed" into the PCB. The process is only analogous to printing. Technically it is quite different.
To carry the analogy to printing a bit farther, let's use the printing of a book as a metaphor for production of an electronic device. The author of the book is the electronics design engineer or "double-E" or electrical engineer. The typesetter is the "layout guy" or PCB designer.