Unlike image files such as jpg and png, pdf files are scaled documents. Correctly printed pdf files will all be of the same size. You can check that your pdf viewer is printing on scale by printing this test file: check_scale.pdf
If this file is not printing on scale, check your printer settings (maybe right click on properties or something) and check your pdf viewer. Make sure you are not printing to fit page. You should be printing to scale.
This is the most common problem. If you are still unsure, email your board. The dimensions of the board - cropped to the outside of your outline will be indicated on the jobcard. Expect these dimensions to be larger than you thought by one outline line width in each dimension.
If a PDF is generated by vector software (eg. pcb design software), and not from a bitmap or scanned image, then it will be a vector file. This means that the resolution is very high, and the file size small.
If you are using a pdf printer driver, adjust the printer properties to the highest resolution (probably 2400 dpi). This may seem strange to set the resolution of a vector file. Doing so ensures highest accuracy in the vectors and does not increase the file size significantly.
It doesn't matter what software you use. As long as it can print to paper you can print to a pdf file.
When you install a pdf printer driver under windows, it is as if you have bought a new printer. Instead of printing to paper you print to a file, a pdf file.
We recommend using pdf995: http://www.pdf995.com/download.html
1) Pdf995 Printer Driver ( pdf995s.exe 4.6 MB )
2) Free Converter . Version 1.5 ( ps2pdf995.exe 8.0 MB )
Once these files are installed on your system you should have a new printer listed.
If you are are using unix, linux, or an apple operating system, you are probably used to printing to file and getting a postscript file. Postscript is an Adobe precursor to pdf. C-Boards will process a postscript file just the same as a pdf file.
Old software like tango, and older versions of eagle also produce great postscript files.