pdfbox extract text by area units

I need to extract the address zip code from a pdf and I use the PDFTextStripperByArea class from pdfbox like in this example ExtractTextByArea. But what are the units of parameters in Rectangle rect = new Rectangle( 10, 280, 275, 60 ); From where must measure and to what units? If they are pixels then it is not convenient to measure pdf page component positions in pixels.