I like to make my own PCB's for projects. Most authors understandably don't share their Gerbers or eagle files, so mostly you get the schematic and a PDF.
This is fine for etching at home, but it's starting to be a schlep with the chemicals and somewhat unreliable results and complexity with 2 layer boards.
This is my method to generate the Gerbers and Gcode nececary to get a good looking PCB first time from the PDF's received.
There are methods to go from Vector PDF's straight to Gerber but it is not reliable or costs a fortune, ECAD packages do not always follow industry standard so results are varied.
This works for me. Here I'm working on a Mark Kelly DC motor control as a PDF.
I take this file and convert it to a 1bit bitmap with 1200 ppi resolution using Illustrator. Take note of the pixel size for scaling later.
Import this file into a Eagle Cad board using the std import bmp ULP. Change the scaling to mm and divide the board width with the pixel width of the BMP to give the correct scaling. should be 0.02112 or there about.
This is the time consuming part but really worth it. Trace the layout using the Eagle Cad tools and make some changes if needed.
Generate the Gerbers in Eagle Cad, I use the Sparkfun CAM processor, as it populates most of the setting for you.
The drill file here is scaled incorrectly, this is because I manually edit the drill file to include the tooling changes. Something Eagle Cad does not do. It will display correctly if you view the std file in Gerbview.
I can now open the Gerbers and Drill file in flat cam ready to generate the Gcode for the PCB milling.
You need to scale the drill file to 2.54 because for some reason Eagle exports drill and board files in metric and imperial. There is no settings to change that in Eagle.
Took a long time to figure this out and I hope it is of some use to others.