Create a new document and specify the size in inches, with a high dpi like 300. (Pic below). Then paste the picture of the CP into that document, using transform (ctrl-T) and holding shift until it fills the document. Be sure to measure everything (measure tool, to find it hold and click on eyedropper) to make sure it matches up with real-world measurements (button holes, etc.).
That is, if I understand what you are trying to do correctly.