iPhones and PDF
Stock standard iPhones handle PDFs well as part of the operating system.
However, they don't give you direct access to the file system so that you can't, for example, create a folder and then copy PDF files into them.
The easy answer is to email PDFs to your iPhone email account. You can then view them by simply tapping on the attachments to the email.
A slightly more elegant way is to use something like Dropbox which is a free download from the App Store. This allows you to synchronise any type of file between your iPhone and one or more computers. The problem is that Dropbox will re-download the file each time you want to view it.
David