Where I live, one cannot buy an Arduino very cheaply. I figure, if I make one for my own purpose on a pcb then it would be much cheaper and would be much more fun. I cannot find any etchable PDF on the internet so can anyone point me to one?
There's a single-sided arduino PCB that you can etch at home:
A smaller alternative is the Really Bare Bones Board (RBBB), it's Arduino compatible and comes with design files:
Or, you could do without a PCB and go for a Paperduino:
In fact, the layout files to (almost) all the Arduino boards are available on their respective pages, linked here: http://arduino.cc/en/Main/Hardware
I would recommend the updated version of the Arduino Single-Sided Serial board, described here: http://arduino.cc/en/Main/ArduinoBoardSerialSingleSided3
I don't believe that the board layout files for the Arduino are available, but you can pick up the design files for the Freeduino here. It's not the Arduino, but it should be compatible enough. I don't know if it's the sort of thing you'd want to etch yourself at home but you're welcome to try. So far as I saw, the boards don't come in PDF format - just Gerber and Eagle, so pick up Gerbv from Sourceforge to convert to PDF.