Can a PDF be constructed from underlying data?

Yes, although the User Interface can construct the PDF for you from underlying data so there may be no need to do it manually.

In detail

Every image product has underlying numerical data associated with it. You can access the numbers in two ways from the UKCP09 User Interface. Either you can produce an image product (e.g. a PDF) and then export the underlying model output that sits behind the image, or you can directly access sampled model output.

The sampled model output is consistent with and can be used to create a PDF (or other image product). However, the User Interface has been designed to do this for you, and you might typically use the sampled model output for statistical analysis rather than for creation of an image product.