Measure up PDF document in pixels

I'm developing a software witch send reports electronicly to tax authority. The data is in form of reports wich is A4 documents with texr and fields. We want to do excacly the same report in WPF and then wee need to measure up columns and rows. We have done that by printing out the document and measure it up with a ruler.

But there are so many reports that printout will overheat the printer ... or almost. I want to find a way which I can measure it up on the screen so I don't need to print out anything.

Is anyone helpful to show me that?