One of the best free apps you should have in your iPhone is the Adobe Reader.It allows you to open PDF documents / eBooks, easily access, manage, and share a wide variety of PDF types, including PDF Portfolios, password-protected documents, fillable forms, etc
Now, in this tutorial I will teach you how to transfer pdf files into your iPhone using iTunes in just a minute.First, you will need to have an iTunes player installed in your pc and Adobe Reader installed in your iPhone( if you didn't know just access your Apps Store, search Adobe Reader, then click Install).
Follow the following steps to continue..
1.Connect your iPhone to your pc
2. Wait the iTunes player to open (If not then find in your desktop the, open it manually).Once open, access the Device menu and you will see every contents of your iPhone like music, videos, apps, ect
3.Just access the Apps tab, scroll down and find Adobe Reader as shown below:
4.You can start adding files to your Adobe Reader by dragging it to the right pane or click the Add button.
5. When done adding files, click Sync button.
6.Now, in your iPhone open Adobe Reader and click the Documents menu then, you will see all files right there.
7.Enjoy reading your eBooks now!