I want to learn PCB design

Sure thing.

Alot depends on the person to be honest. A background in electronic design is beyond helpful. You would need to understand or have a feel for basic electronic components and how they are connected to form a circuit which is commonly called a schematic. You should also be able to read a schematic and understand things like power and ground. Assuming no prior knowledge there is a very good book that will walk you through the process.

Have a look for "The Design & Drafting of Printed Circuits" third edition 1984 by Lindsey - Published by Bishop Graphics INC.

The book will walk you through the concepts. The book is old but excellent.

The best advice I can offer is learn how to design a PCB the old fashioned way using tape and mylar film as opposed to diving into a cad system. The actual board does not have to be complicated at all but if you create the board by using tape and transfers you will gain an understanding of scale without using a PC. You will also have to be creative in how you lay out the tape and find clever ways to work around pads for the components. It sounds insane right when one considers that today we have slick cad systems to do the work but the concept is to see and understand. When you move to a cad system you will have the basics under your belt and yes you will fully appreciate modern cad to assist in designing that board and doing things like creating ground planes etc. Tape & Mylar is what was used before cad systems came along. All the PCB
designs had to be done by hand to create a master from which a repo camera created a film or photo copy of the board design. That book I mentioned above covers how it used to be done and also using Cad or Cadd as it was called back then.

Other things you could do is visit a local PCB house if one is in your locale, doing that will show you how the physical board is created.

Best of luck

Paul