Q: How do I access documents on my iPhone?

I need to know how to access PDF files stored on my iCloud drive from my iphone.  For example, I put travel documents into my iCloud so I could access them while traveling, but have no idea how to get them on my phone now that they're in the cloud!  I am using iOS8.4 on my iPhone, and version OSX.10.3 on my macbook pro.