No keyword with name 'From Pdf' found

This is odd. I am not aware of any special structure. Maybe it is something simple, like line formatting.

I find the double usage as Variable file and Library suspicious. It never occured to me to try this:

*** Settings ***
Library    PDFReturn.py
Variables    PDFReturn.py

I use separate files for these purposes.

Also: i use libraries with in capital letter as class library not as module library. Not sure if python or robot have a similar assumption. I would try to build it like that and rename the library:

Library    pdf_return.py
Variables    configuration.py

Module libraries cannot be shared with other projects, therefore I hardly ever use them. Class libraries have the same implementation effort, but they can be easily transferred in to a separate library project:

from robot.api.deco import library

@library
class PDFReturn:
    var1 = none
    var2 = none

    def from_pdf (self):
        self.var1 = some data from PDF file
        self,var2 = some data from PDF file
        returnVariable = (var1, var2)
        return returnVariable

Maybe the thoughts help.