A GeoPDF has latitude and longitude coordinates built into it, and your phone or tablet can get its position from satellite. An app on your portable device can bring the two together in real time, to show your current position on top of the PDF.
In order to take advantage of the geospatial capabilities of a GeoPDF, you will need an application that allows you to plot your position on top of the PDF, and track that position in real time. This comes in the form of "apps" on portable devices such as smartphones and tablets. A common GeoPDF reader is Avenza's PDF Maps App, available for both Android and iOS operating systems. There are several apps that allow you to do this (PDF Maps, Global Mapper, TerraGo Mobile, etc.)