PDF files
containing the PCB artwork are generated for an A4 paper size.
When
printing the artwork you should ensure that the printer driver does
not re-size the document to fit the printer / paper size you are
using. Check that page scaling and document sizes are correct
before printing even if you're paper size is set to A4.
I also
recommend printing a test copy onto plain paper, then place the PIC
microcontroller IC onto the printed artwork to make sure the pins on
the actual chip align with the pads on the artwork.