I think the question will eventually boil down to in what format you need the pathway information and what are you going to do with it; but if we put these concerns aside, I suggest you use Pathway Commons 2, where multiple data sources such as NCI PID, Reactome, Phosphosite Plus, Panther and so on are being normalized and merged in a nice way. On the home page you will find a few tools that will facilitate your access to this resource or you can use the webservices to extract what you need:

http://www.pathwaycommons.org/about/

As a side note: NCI PID is going through a re-planning period and although it contains some parts of the Reactome, they are really old; whereas on PC2, you will get the whole up-to-date Reactome data. Disclaimer: I am a PC developer and somewhat self-promoting here -- but for a good reason :)